Talk:Energy efficiency in transport/Archive 1

Lead in paragraph
Could someone please wikify by writing a lead in paragraph? 199.125.109.98 17:30, 20 June 2007 (UTC)

Urban and Long-distance Figures
It's extremely important to differentiate fuel consumption for different modes of transportation across distances. An airplane travelling 150 and 800 km would probably have different consumption per passanger-kilometre. Urban consumption for motor transport is generally much higher than the table indicates, and this is likely where most passenger transportation takes place these days. I bet TGV trains are not any use for short intervals between stops. Bicycling and especially walking tend to cover shorter distances, growing increasingly slow and irrelevant with trip length.

People seeking a comparison for commuting purposes would be disappointed, if not deluded. I know I am. Z-d 06:55, 31 October 2007 (UTC)

US Automobile Avg MPG Inconsistant
In the data summary it states US Automobile avg mpg as 38. In the citation is states "US fleet mileage averages 23 mpg, occupancy avg is 1.57" Which figure is accurate? Is this a citation or a correction? Confused... — Preceding unsigned comment added by 68.77.72.142 (talk) 01:31, 13 November 2007 (UTC)

Steamship?
Does anybody use these for water transit any longer? The inclusion seems silly even if nobody has ever done a study of the efficiency of hovercraft and diesel ships. Z-d 07:04, 31 October 2007 (UTC)

I also does not see steamships for people transport (may be for payload in an undeveloped country) but also is missing the MOTORCYCLE, more demanded owing to the trafic. 10/03/08 —Preceding unsigned comment added by 189.181.113.183 (talk) 21:09, 10 March 2008 (UTC)

more messy units
the tables list "miles per gallon per passenger". This should be "passenger-miles per gallon". — Preceding unsigned comment added by 131.111.79.111 (talk) 17:52, 30 November 2007 (UTC)
 * Shouldn't be miles/gallons anything as primary unit anyways, should be using SI as the wiki preferred measurement units since this is not a US specific topic. As mentioned below it is ambiguous and confusing as it is. — Preceding unsigned comment added by 212.30.195.50 (talk) 03:25, 9 January 2008 (UTC)

"It should be noted, however, that the actual fuel efficiency of human power is in dispute. Recent articles have pointed out that "human power" should include the cost of food production, which can be quite high for energy-intensive diets. ."
 * I removed this from the main page because it's not a life-cycle page. Peanut butter or even simply vegetable Oil is easily comparable to Ethanol or BioDiesel.  Ephdot (talk) 13:52, 21 March 2008 (UTC)

"The claims by Chris Goodall suggest that walking consumes about the same amount of fuel as driving in some societies, thus the posted human-power efficiencies may be inflated by up to an order of magnitude. It should also be noted that passengers using other modes of transportation also consume food. And, not necessarily less food than those using human power. This brings into question the validity of including food production energy costs in human power efficiency calculations."
 * If driving consumes as much energy, this means that the driving task uses energy which should require adjusting the car values, not the human values. This sort of hair splitting seems unnecessary. Ephdot (talk) 13:52, 21 March 2008 (UTC)

A380
According to A380 specification numbers and accounting for jet fuel we get not "less than 3 L/100 km" as stated on their other page...weird. Ephdot (talk) 02:54, 23 March 2008 (UTC)
 * To arrive at that 4.4 figure you must have assumed that there is no safety margin in Airbus's specification of range, and that the plane uses the last drip of the 310,000.0 litres of fuel in its tanks as it taxis to a halt after travelling 15,200.0 km, and with 525 passengers. Their 'official' fuel consumption figure will be more standardised than that, as the figures for automobiles are, with probably a maximised (555?) passenger occupancy. -- de Facto (talk). 09:26, 23 March 2008 (UTC)
 * The advertising page with the "less than 3.0L/100 km" is not specific about anything. It uses a weasel number "less than 3.0", it doesn't specify if it's based on average loads or fully loaded planes, it doesn't say if it includes take-off and landing or if it's "just" cruising fuel use...  It's not specific.  At least using a range and fuel capacity number gives you a (perhaps conservative) number, but not a grossly inflated (deflated) one.  We'll have to wait for real use numbers to know for sure... Ephdot (talk) 13:33, 23 March 2008 (UTC)
 * If you can find a better number from a reliable source, then use it and cite it, but you shouldn't calculate it based on unreliable assumptions. For now, the Airbus figure is the best we have. -- de Facto (talk). 17:33, 23 March 2008 (UTC)
 * Even if you take 10% as "left in the tank", it's above 3 L/100 km. I'd be happier to see actual numbers and assumption they made before quoting it when other numbers show it's unlikely. Hmmm, it works if you use 850 passengers, but no compensation for weight. Luggage?   Interesting discussion here: http://blogs.law.harvard.edu/philg/2007/03/19/airbus-a380-more-fuel-efficient-than-a-toyota-prius/  Ephdot (talk) 18:34, 23 March 2008 (UTC)
 * I've added a comment from CNN, clarifying the Airbus claim slightly. It says the A380 achieves 2.9 L/100 km per passenger, based on 555 passengers with no luggage or cargo.  I wonder what allowances the U.S. EPA, or the UK VCA make for luggage and cargo when calculating car fuel consumption. -- de Facto (talk). 21:20, 23 March 2008 (UTC)
 * The big drain for cars is A/C, not so much weight. EV range can drop by 50% with A/C on.  Ephdot (talk) 02:21, 24 March 2008 (UTC)

Caveats
The "Caveat" section should be placed at the end and looks like it was written by an auto lobbyist. Lequis (talk) 21:07, 21 March 2008 (UTC)
 * Some of the sections were there originally at the top and I didn't remove them. They seem a bit redundant now.  I put them at the top because the following section is messy and misleading for the reasons given.  Transit train numbers in the 500 passenger mpg range are just outlandish given actual numbers are more in the 70 mpg range in the best of circumstance (UK).  Intercity numbers in that range (TGV) are more plausible.  Any more specific suggestions? Ephdot (talk) 01:58, 22 March 2008 (UTC)

Addendum. There is no way in hell that an aircraft can travel 100km on 3L of fuel. Per person? Even 300L of fuel to travel 100km seems specious. Clarify? Lequis (talk) 21:10, 21 March 2008 (UTC)
 * I didn't add that reference and haven't scrutinized it yet. There are just so many that are questionable... Ephdot (talk) 01:58, 22 March 2008 (UTC)

"* In most developed countries, most of the electricity does come from fossil-fuelled power plants. These are typically 35-40% efficient. So exercise caution when comparing, say, liquid-fuelled cars to electric trains (or to electric cars). The energy consumption quoted for the electric train (or the electric car) often excludes all the generation losses. "
 * Most of this is contained in the MPGe paragraph. Ephdot (talk) 02:53, 22 March 2008 (UTC)

This is a biased methodology and is disputed. I propose to delete any figures from those sources. Please only include third party sources which show the source of fuel, loads and methods. If comparisons are made please cite approved methods and sources not include your own. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:25, 24 March 2008 (UTC)
 * I did. I used MPGe.

In that case you should also include losses bring liquid fuels to market: EG road tankers, distribution points. It really depends on the country concerned on the losses, France/Switzerland are mostly Nuclear/Hydro, UK is 32% coal. These losses could be substantially reduced using distributed power supply systems and, for example, wind power on a per GW/H basis. —Preceding unsigned comment added by Robthoburn (talk • contribs) 14:57, 24 March 2008 (UTC)
 * Addressed in the Standardization section Ephdot (talk) 15:25, 24 March 2008 (UTC)

ATOC quotes per passenger figures per CARRIAGE (car), not per train as the government figures quote. Some train loads are substantially ABOVE their 100% seating capacity, in many countries on certain runs. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:10, 24 March 2008 (UTC)
 * The reference gives the average, not "in special circumstances" . Ephdot (talk) 15:25, 24 March 2008 (UTC)

While the mean average could be accepted at 33% (I believe it's 35% now) nevertheless the caveat is yield management is producing significantly higher runs on intercity runs (typically 50-70%, similar to airlines) - which is reflected in the choice of 70% for pendolino services and as is higher for commuter trains into conurbations, covered by the other quoted trains. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:10, 24 March 2008 (UTC)
 * The 33% and 35% numbers need references. Some specific rail lines do have high numbers and it's OK to cite those.  It's not OK to generalize based on a single rail line.  Ephdot (talk) 15:25, 24 March 2008 (UTC)

33% is provided by ATOC, please check with them. You may recalculate showing 33% for the others trains and 51% for the pendolino, and 65% for regional short haul as they can be substantiated if it bothers you that much. Please do not recalculate showing fictional fuel sources/transmission losses and over generalisation. You may however add that power losses could be included for both rail and road, provided you can cite sources and show approved methodology and state that this is a function of the transmission/energy supply system rather than of individual vehicles. Else I will be deleting it, because frankly it's misleading.

This is however a theoretical table in any case, as figures for each individual car/plane/train types are not specifically available. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:10, 24 March 2008 (UTC)
 * The whole table should be removed then. We want real numbers, not guesses.  Ephdot (talk) 15:25, 24 March 2008 (UTC)

The idea of a theoretical table is to provide a comparison. You seem to be changing figures to make one form of transport look bad and adding your own biased comments. I have provided frequent sources on various cases and these have been deleted. This attempts to mask the whole picture as it has been made quite clear on average figures- which do not reflect real life and are therefore misleading. It is important to show the WHOLE picture from NUMEROUS sources in different countries. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:37, 24 March 2008 (UTC)

Also don't forget loads are brought down by competing methods of transport, so quoting the fuel efficiency for say a rural bus or train, is actually often the result of car transport taking passengers away, and making the overall figures less favourable and less efficient overall. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:10, 24 March 2008 (UTC)
 * I don't follow how competition plays into actual fuel efficiency figures. Ephdot (talk) 15:25, 24 March 2008 (UTC)

"* Electric motors are often used to drive vehicles because they can be finely controlled, they deliver power efficiently and they are mechanically very simple. Electric motors often achieve 90% conversion efficiency over the full range of speeds and power output and can be precisely controlled. Electric motors can provide high torque while an EV is stopped, unlike internal combustion engines, and do not need gears to match power curves. This removes the need for gearboxes and torque converters. Electric motors also have the ability to convert movement energy back into electricity, through regenerative braking. This can be used to reduce the wear on brake systems and reduce the total energy requirement of a trip. Electric motors also do not produce greenhouse gases unless, of course, the source of electricity for the motor, such as a coal power plant, produces greenhouse gases."
 * This paragraph seems more suited to a discussion on fuel efficient automobiles in particular. Ephdot (talk)

Misleading numbers

 * Combino light rail (recalled )
 * 510 mpg (estimate)
 * 1400 mpg
 * 1400 mpg

These trains don't run anymore and the number are based on a trial period and not actual use.


 * Colorado Railcar
 * 330 mpg
 * 470 mpg
 * 470 mpg

Website claims 2.5 better economy which would bring it up to ~40 MPGe * 2.5 = 100 mpg, not 330 mpg.


 * BART commuter train
 * 244 mpg
 * 520 mpg
 * 520 mpg

http://www.bart.gov/about/reports/congress.asp 97 million trips/year 13 mile average trip length 3 million/month in electricity 360,000,000 kWh - assume 10cents/kWh

360000000/(97000000*13) = 285 Wh/passenger mile 285 Wh = 972 BTU 125000 BTU per US gallon/972 BTU * 1/3 efficiency factor = 42.5 passenger mpg

"During the lowest day time ridership hour in the midday lull (noon – 1PM) BART averaged 360 watt hours per person-mile (wh/p-m). From 4-5PM the average was 251 wh/p-m  and from 5-6PM it was only 171 wh/p-m. " www.ilsr.org/pubs/savingsbartreport.pdf These are not average numbers.


 * Clean Air Express (bus), Santa Barbara, CA, USA
 * 230 mpg
 * 330 mpg
 * 330 mpg

No references.


 * Airplane
 * 67 mpg
 * 85 mpg
 * 85 mpg

Not average passenger mpg, based on specific (unnamed) aircraft mpg? Ephdot (talk) 00:53, 21 March 2008 (UTC)


 * GM EV1 Electric Car (recalled)
 * GM EV1 Electric Car (recalled)


 * EV1 numbers were not from charging efficiency - 373? Wh/mile plus the vehicles was recalled. Ephdot (talk) 14:49, 22 March 2008 (UTC)

" The UK DfT state the following figures for public transport in 2005 :

"
 * The table above is from a Hansard (a secondary source) I wasn't able to trace to original research. I found better numbers but they were deleted by an unnamed source.
 * | 18.5


 * 182 mpg is an VERY high number and so needs better proof than a secondary source. Ephdot (talk)
 * 182 mpg is an VERY high number and so needs better proof than a secondary source. Ephdot (talk)

I propose to delete the whole table going by that argument the figures for other modes are unsubstantiated. Only please do not edit and compare US gallons to UK gallons as this is misleading. —Preceding unsigned comment added by Robthoburn (talk • contribs) 14:42, 24 March 2008 (UTC)
 * I agree the table should be removed. Ephdot (talk) 15:44, 24 March 2008 (UTC)
 * MPGe templates allow straightforward conversions from imperial and us mpg and diesel to L/100 km and the MPGe number. The tricky one is electricity. You want it in kWh/passenger km or MJ/passenger km?  Ephdot (talk) 15:44, 24 March 2008 (UTC)

Edit war
I have reverted to revision 200391091 by DeFacto dated 23 March 2008 22:20 (UTC) due to the recent edit warring. If this edit war continues, I'm going to recommend that the the article page be protected. For the future, please discuss major edits that are likely to be controversial on this talk page. Thanks. Lightsup55 ( T | C ) 20:36, 24 March 2008 (UTC)

Help with 'UK Transport vehicle comparison' table
Can anyone explain the contents (meaning and units) of the 'Oil/Ltr/Mile' and 'Oil/Gal/Mile' columns in the UK Transport vehicle comparison table? -- de Facto (talk). 17:44, 25 March 2008 (UTC)
 * I vote to move the table to this page and put the validated entries back into the list section. Ephdot (talk) 00:58, 27 March 2008 (UTC)

Comments moved here from DeFacto's talk page
"Why not put it into the 'Train' section" - the paragraph I wrote seemed self evident - rail systems and bus systems waste energy because they must stop frequently. The reference was specifically for rail, but applies to buses and other re-used vehicle systems.

WP:or's first sentence ends with "...that serves to advance a position." - I think that though I hadn't provided references, personal experience will validate the observations. The MPGe also falls into this category. Even though there is no agreed upon standard for conversion of GGE to kWh (for example) explicitly setting a number for comparison purposes on a page isn't advancing a position - just enabling a comparison. If I could program the site, I would make the number a variable the user can enter themselves. 36 kWh for some, 11 kWh for others. Asking people to do math seems too onerous a demand... ;-) Ephdot (talk) 15:44, 25 March 2008 (UTC)


 * Point 1. The comment was about trains, and the reference was train specific, so I thought the 'Trains' section was more appropriate. -- de Facto (talk). 16:10, 25 March 2008 (UTC)


 * Point 2. Basically, comparisons and analysis of data should only be from reputable and cited sources. Raw data, and conversion factors, if from reliable and cited sources, are OK - readers can make their own comparisons and draw their own conclusions. -- de Facto (talk). 16:23, 25 March 2008 (UTC)
 * The "UK Transport vehicle comparison" table must go or be fixed. It cites mpg from an AC train which can't be done right now.  In fact, all mpg and L/100 km numbers from electric vehicles should be removed since there is no recognized way of converting those numbers.   Ephdot (talk) 17:42, 25 March 2008 (UTC)

UK Transport vehicle comparison

Note:

* Some trains are equipped with regenerative braking which can save a further 20% of energy.

** Plane fuel consumption is based on the average figures, in reality there is greater fuel consumption initially due to the increased weight in fuel yet to be burnt off.

This messy table was moved so that reference can be reinserted (if needed) into the list when validated. This table makes conversions to and from electricity to fossil fuel equivalents which are not agreed upon. Ephdot (talk) 13:11, 30 March 2008 (UTC)

Fuel Economy infobox
In a related matter, does anyone think that fuel economy should be kept out of the automobile infoboxes? Please voice your opinion at http://en.wikipedia.org/wiki/Template_talk:Infobox_Automobile#Vote_on_Fuel_Economy_in_the_Infobox 198.151.13.8 (talk) 18:28, 7 May 2008 (UTC)

Table move
Many of the entries in the list of transportation fuel efficiencies are incomplete, based on guessed numbers and from advertising pages that frankly misrepresent information. The table was a sifted version of these entries free from questionable entries. It was at the top and on the right side in a prominent location. By placing it at the bottom and calling it a "summary" page, we've put the weak information first with the best, most reliable information last. Ephdot (talk) 14:27, 23 March 2008 (UTC)
 * We should eliminate "guessed" numbers, and "weak" information altogether. All data, in the text and in the table, should be from reliable sources, with the context stated if appropriate, and properly cited. -- de Facto (talk). 17:36, 23 March 2008 (UTC)
 * So, what do we do with misleading references like the A380 one? Their numbers are completely without context or justification.  I tried to point out that the entry was more likely a cruising number in the page (not indicative of fuel efficiency - my car can get 100 mpg if I drive it at 10 mph without stopping - who cares?) and it was reverted.  Do we take it out or leave the quoted and referenced BS in wikipedia? Ephdot (talk) 18:05, 23 March 2008 (UTC)
 * To criticise Airbus's numbers, a significant view that they are wrong needs to be found and cited. Original synthesis is not allowed - see WP:OR. -- de Facto (talk). 20:15, 23 March 2008 (UTC)
 * Nice find on the CNN piece. (this should have be in the A380 section...) Ephdot (talk) 02:16, 24 March 2008 (UTC)
 * I still believe there should be an overall table. There should be a "picture is worth a thousand words" type of thing at the top. That is why presentations were invented. When I went to that page, the first thing that struck my eyes was the table. I instantly saw that getting around with a bicycle is more efficient than walking, and there are even some non human powered means, such as electric cars and electric trams that beat walking in the efficiency respect. So how do I want to get transported, which means should I seek to get around? It's hard to tell from the page currently, it's a lot more ambiguous without the table, even if the data is technically there, I think it's less readable. Yes, there will always be minute details in the accuracy of the numbers that go in a table, you're always going to be comparing apples to oranges, but one gets an overall picture very quickly, and that's important. If anything, extend the ranges so they overlap heavily. I would even consider a table with data that went for bicycles 50-650 mpg, for airplanes 5-200 mpg, and similar, for cars 5-200 mpg. There is no correct answer, because there are some cars that get less than 5 mpg, and some competitions where cars get well over 200 mpg, but there is that "guessed" number between 15-60 mpg that's common sense. I don't mind the guessed numbers, especially when the category of what a "car" is is vague too, then so should be the mpg value for it, somewhat vague. Who is going to ride around in a http://www.ecomodder.com/blog/2008/03/15/super-mileage-competition-nets-7148-mpg/ super efficient car. That's not the status quo. When the world's definition of a "car" becomes that 7000 mpg device, then we can update the table with a 7000 mpg "guess" for cars. In the meantime, while a "car" means what it generally means to people today, the current values in the table were fine. I think that a table ranking the modes of transport based on fuel efficiency, is the most valuable thing to have on that page, it provides a quick glance starting point and mental framework to reading the rest of the details on the page. Please add the table back. Sillybilly (talk) 16:43, 15 May 2008 (UTC)
 * I've no problem with a table &mdash; so long as it is from a reliable source, its context and assumptions are explained, its units are homogenous, and it is properly cited. The table that I removed was appartently a jumble of unsourced numbers and original research. -- de Facto (talk). 17:01, 15 May 2008 (UTC)

The road, rail and air UK figures come form approved or respected sources for the most part. The exception is air transport which has been calculated using averages based on fuel capacity and range. —Preceding unsigned comment added by Robthoburn (talk • contribs) 16:19, 24 March 2008 (UTC)
 * No, it's a direct reference now. see A380 discussion. My calculations gave it more litres per 100 passenger km...  Ephdot (talk) 16:26, 24 March 2008 (UTC)

Table
What's up with someone removing the table? It is essential to have a quick reference that shows the different spectrum of fuel efficiency. And don't go telling me that you can't compare walking and running with automobiles, because you can - you just do an equivalent energy conversion. Also, it is not practical to include conversions, unless there is only one value (no separate avg occupied vs max occupied numbers). It's like meticulously adding British English/American English transcriptions to an article (The labor (labour) involved ...), or editwarring over which to use, AE or BE. Pick one, mpg or L/100km, I chose mpg just because it was less characters to write, and frankly, I would check to see if this article was written in BE or AE and use whichever corresponded (they don't use the English system in England, but use the metric system instead, and America doesn't use the metric system, but uses English measures, go figure). And don't waste your breathe telling me that you can't convert from an electric traction motor to mpg gasoline, or diesel fuel to gasoline mpg. Just make the conversion and put it into the table, and put the table as float right next to the TOC. If it is too long, use to keep it away from other text if you need, or just chop out a few rows - it doesn't need to be inclusive, but it does need to show the spectrum of fuel efficiency, which as I recall, runs from bicycle at the top at about 600+ mpg to helicopter at the bottom, at about what was it, 4 mpg? And no edit warring. Discuss first. 199.125.109.49 (talk) 22:33, 15 May 2008 (UTC)

Wikipedia's automatic unit conversions are incorrect!
"The General Motors EV1 was rated in a test with a charging efficiency of 373 Wh-AC/mile or 0.6 kWh/100 km.[12] The four passenger GEM NER also uses 169 Wh/mile or 0.3 kWh/100 km ,[13] which equates to 0.1 kWh/100 km for four passengers, albeit at only 24 mph (39 km/h)."

As a prelude to my main point, what is a W·h-AC? I'd never heard of it before, and the only people who seem to use it are the US DoE's Energy Efficiency and Renewable Energy division (as in the linked electric vehicle performance sheets on the main page). A watt is one joule per second. It doesn't matter whether that joule of energy is supplied by DC or AC, petrol, elephant dung or hamsters in a wheel: 1 J/1 s ≡ 1 W. Could someone explain?


 * They mean that the charging efficiency applies to charging via the mains AC power, they mesaured the inefficiency of the charger and factored that into the 373 Wh/mile figure.

Anyway: the conversion factors for the GM EV1 appear wrong. Assuming that 373 W·h-AC/mile is the same thing as 373 W·h/mile, then the convertion to SI is 373 W·h/mile * 0.6214 mile/km = 232 W·h/km. Yet the quoted figure is 600 W·h/100 km which equals 6 W·h/km. It's apparently out by a factor of 39. Similarly for the GEM NER, 169 W·h/mile = 169 * 0.6214 W·h/km = 105 W·h/km, which is 10 kW·h/100 km, not 0.3 kW·h/100 km.

The reason for the error appears to be that the figure in W·h/mile is divided instead of multiplied by 0.6214 (producing 2.56 times the correct figure), and then the "100" in the "100 km" denominator is ignored (producing 100/2.56 or 39 times the correct figure). But I see from the page source that this error is introduced by a Wikipedia conversion tool. Assuming I'm right, of course, how can this be fixed?


 * By not using the conversion tool? As I understand if the conversion tool will now be smart enough to convert because of the number of things going on.

Can I also add my forlorn plea not to use gallons (and other customary units) in an article which is of international rather than just US relevance? Even in the UK, children are educated exclusively using SI units (including me, and I was born in 1973!), petrol is sold in litres, and transport reports invariably talk of kilometres not miles. And I didn't even find out until the recent oil price rises that a US gallon isn't the same thing as a UK gallon! It just seems to be asking for trouble from non-US readers who almost without exception will not understand US or imperial units, and will be very unlikely to be aware that the two are not the same. Peter Barber (talk) 13:17, 29 May 2008 (UTC)

Freight shipping
The article really, really needs information on freight shipping by sea.- (User) WolfKeeper (Talk) 05:58, 31 March 2008 (UTC)
 * It's an odd misconception that water freight is cheaper than rail. However, it takes something like 30 to 50% more energy. 199.125.109.49 (talk) 00:21, 16 May 2008 (UTC)
 * References???- (User) WolfKeeper (Talk) 21:57, 19 May 2008 (UTC)

Fuel cost per unit mass for shipping via large tanker is lowest. See: http://www.bentham-open.org/pages/content.php?TOEFJ/2008/00000001/00000001/11TOEFJ.SGM —Preceding unsigned comment added by Ergophile (talk • contribs) 04:40, 15 June 2008 (UTC)

disagreement between methods and tables
I propose if the disagreement over methodology continues to show only links to other respected sources which have a degree of expertise and discard all tables. —Preceding unsigned comment added by Robthoburn (talk • contribs) 16:07, 24 March 2008 (UTC)
 * So we leave all electric references in kWh/passenger km or MJ/passenger km? Any preference? Ephdot (talk) 16:19, 24 March 2008 (UTC)

I propose to remove all electric sources as equal comparisons could be made with gasoline, diesel and kerosone and getting that to the point of use if you propose losses. This is pointed out in the RSSB document link at the bottom.

The reality is the is no one method available for calculating power losses because it depends on many localised factors, including the localised power supply situation, overhead catenary supply points and voltage.

If you wish to delete ALL tables that's fine by me and provide only links to third party sites where information has been taken from official sources (showing those sources) and the methodology used.

Loads are also equally variable, and where I think it is okay to show a theoretical load or references to actual loads, over generalisation is not especially helpful unless it is shown that is is a mean average load and why that occurs and the circumstances for it.

I also propose an environmental transport page showing CO2 and other pollutants and fuel efficiency is not a good guide to environmental damage. —Preceding unsigned comment added by Robthoburn (talk • contribs) 16:30, 24 March 2008 (UTC)


 * I kinda liked having a table with fuel efficiency comparisons laid out. I think "kWh/passenger km" for electric vehicles would work with the MPGe number in parenthesis.  Then there is no confusion over electricity vs litre equivalents.  Ephdot (talk) 17:02, 24 March 2008 (UTC)
 * If we decide to go with "kWh/100 km", I can move the CO2 examples to the MPGe page, perhaps with a specific remark to the effect. Looks like they use "kWh/100 km" here too: Low-energy vehicle Ephdot (talk) 17:21, 24 March 2008 (UTC)

e.g.:

Summary


I think it's misleading. For example, the French TGV is powered by Nuclear/Hydro. What do transmission losses prove? after all the end user buys what they use, not the losses. The losses are the power supplier problem, not the transport users.

If we are comparing environmental damage based on CO2, then clearly the figure is misleading compared to say an airplane which has to run on AVgas. Indeed, according to the IPCC pollution at height us on average 2.7 worse than on the ground. —Preceding unsigned comment added by Robthoburn (talk • contribs) 17:19, 24 March 2008 (UTC)


 * Transmission losses? The whole system energy use should be included to compare one mode of transportation's "fuel" efficiency to another.  So kWh/100 p&middot;km includes line losses on the rail lines, but not from the generating station.  Those are taken into account on the power generation side.


 * I agree about the pollution argument. We could add it to the caveats because it's an important point to consider.  In that respect, using MPGe for CO2 would require an extra factor.  Is there a GHG equivalent factor for height already defined?  Ephdot (talk) 18:00, 24 March 2008 (UTC)

I would suggest that tables are removed and only links provided to studies, which take into account specific circumstances and look at the end user.

By all means concentrate on MPGe on a separate page. I'll look to compile and environmental page shortly, which takes account of specific pollutants, and studies into for example, food miles, whole life energy costs and their pollutants and effects. I still hold the opinion that MPGe is too simplistic for this purpose and/or costs to the end user. The environmental argument is a complex area, and it needs balance as well as references to the impact of certain fuels like biofuels.


 * If you sign your posts, I won't have to wait for the signbot to do it. What happens with silly conversion numbers like kWh to BTU based on gasoline BTU content?  That's just wrong!
 * You mean copy numbers from the fuel efficiency page to the MPGe page and make comparisons there? That could work.  I'd like to get some input from others too on what to do. Ephdot (talk) 18:37, 24 March 2008 (UTC)

' What happens with silly conversion numbers like kWh to BTU based on gasoline BTU content? That's just wrong!'

Normally 1 gallon US gasoline = 36.6kw/h not 11 kwh/h, which on the fact of it is plane wrong applied in the way it's being applied. —Preceding unsigned comment added by Robthoburn (talk • contribs) 19:58, 24 March 2008 (UTC)


 * NO! It doesn't work that way. There exists no machine to convert 100% of the energy in a US gasoline gallon to electricity.  Also, Solar power uses zero fuel so why stop at "36.6kw/h"(which is wrong BTW), why not go to Billions of kWh?  It simply makes no sense.  Ephdot (talk) 20:16, 24 March 2008 (UTC)

I never said the machine needs to convert 100% of the energy, we are talking about fuel use within a vehicles to do a set task. We already have the fuel use figures for every mode, albeit using different fuels.

It is important to the end user how much electricity/kerosene/diesel etc it takes go 100/km. Additional losses in the power generation scheme are a diversion. Besides these are already included in the ATOC figures.
 * Electricity isn't a fuel like gasoline is a fuel. Electricity has no energy content.  A chemical battery has energy, and a solar panel generates energy by converting the sun's energy... Ephdot (talk) 20:53, 24 March 2008 (UTC)

Nevertheless, we already have the figures for how much Kw/h needs to drive a vehicle over 1 mile, which does have an equivalent energy content (in BTUs or joules). No further reductions are required, internal losses are accountant for. Robthoburn (talk) 21:03, 24 March 2008 (UTC)
 * If you're trying to say the ATOC based numbers in the link below should be included, I agree. The only adjustment is to account for Diesel's higher BTU content.  Ephdot (talk) 21:08, 24 March 2008 (UTC)

http://www.atoc-comms.org/admin/userfiles/Baseline%20statement%20-%20FINAL%20-%20Print%20version.pdf

and in the appendix

Carbon dioxide emissions from electric trains have been calculated from ATOC data on train electricity consumption (adjusted for losses in the high voltage national grid and losses in the rail electricity distribution network). Information on the emissions from major power stations has been taken from the NAEI and combined with information on electricity generated from major power stations and renewable generators from the Digest of UK Energy Statistics (DUKES, 2006).

Robthoburn (talk) 20:30, 24 March 2008 (UTC)


 * A nuclear submarine has an on-board power source and uses uranium as a fuel. What's the equivalent in gasoline?
 * The average engine probably outputs 34% of it's fuel as useful energy. That's about 11 kWh per US gasoline gallon.  After that, the efficiency of the vehicle to convert this power to forward motion is the efficiency that really matters.  It's drag coefficient, it's rolling resistance, it's mechanical efficiency, it's weight etc...  Using a 34% efficiency factor allows us to compare all these other factors in a more or less even fashion. Maybe we can think about it as converting heat engine output to electrical equivalent using a very dirty plant - the engine?  Ephdot (talk) 20:43, 24 March 2008 (UTC)

Then you are misreading the stats. The stats already include the losses within the machine, and gives the amount of fuel that is required to go a set distance. You do not need to reduce this number any further. Robthoburn (talk) 20:48, 24 March 2008 (UTC)


 * The ATOC stats are for diesel engines so conversion to gasoline equivalent is easy. I'm talking about electric trains and electric cars.  Regular cars for example, convert gasoline at about 11 kWh per US gallon of gasoline.  That number is a good number to use to compare electric automobiles with regular automobiles and Diesel/gasoline equivalent trains with electric trains isn't it?  Ephdot (talk) 21:00, 24 March 2008 (UTC)

Yes but electric trains/cars are much more efficient at converting that energy to tractive effort! All we need to know is how much kw/h are needed to power it. Of course there are different efficiencies in generating electricity, or drilling for oil for that matter, but selective uses of a losses are misleading and incorrect. Robthoburn (talk) 21:08, 24 March 2008 (UTC)
 * Yes, so why not use a single number, 11 kWh everywhere to make comparisons? You will see that the lighter, more efficient electric vehicles will be better, but not by a factor of 3.  3X is just not reality.  Ephdot (talk) 21:13, 24 March 2008 (UTC)

Because the 11kw number is a gross generalisation, highly biased and distorts true costs and environmental performance. Robthoburn (talk) 21:20, 24 March 2008 (UTC)


 * Untrue. You think "36.6 kw/h" is fair? It outlandish.  Ephdot (talk) 21:25, 24 March 2008 (UTC)

It's irrelevant to the end user paying the bill, the figures quoted are what they are paying for! I note you also have not made proposals to include the regen braking saving, and instead put in a remark about stopping is inefficient, even though the potential energy of the vehicle is converted to useful tractive effort for other vehicles or stored on board in the case of a hybrid car. Robthoburn (talk) 21:30, 24 March 2008 (UTC)
 * You're changing the subject. Please justify "36.6 kw/h" per GGE.  Ephdot (talk) 21:37, 24 March 2008 (UTC)

That's the standard agreed energy conversion. In theory 36.6 kw/h will do exactly the same work as 1 US gallon of gasoline (say heat a certain amount of water to a set temperature) which is what we are interested in, not adding the losses of inefficient ICEs into calculations to compare vehicles using electric motors. Robthoburn (talk) 21:52, 24 March 2008 (UTC)
 * There is no standard. Heat and power are different. Converting one to the other isn't 100%, it closer to 34%.  It's not adding losses, it's making a good comparison.  What's the point of giving electric power a 3X advantage (without any justification) unless you're selling something?  What are you selling?  Ephdot (talk) 21:59, 24 March 2008 (UTC)

I'm not selling anything! While of course heat and power are different, the actual efficiency of conversion should be taken on a individual basis - which is why there is no agreed standard for what you are talking about! Harnessing energy from wind power, nuclear power and hydro power is extremely efficient especially using a distributed grid. Gasoline is merely stored sunlight, you still however need energy (which btw can increase in time) to get it out of the ground and to your car, and then burn it in a inefficient ICE. You are comparing apples and oranges, we are interested in the end user cost for the vehicle Robthoburn (talk) 22:11, 24 March 2008 (UTC)
 * No, we are interested in fuel/energy efficiency in transportation, not $ or CO2 (these are a bonus). Ephdot (talk) 22:17, 24 March 2008 (UTC)
 * You are referring to life cycle cost, a different topic. Ephdot (talk) 22:20, 24 March 2008 (UTC)

That's why it must be done on a individual basis, and not aggregate the figures to use only one part of the energy conversion process. 34% is not a fair comparison because in certain circumstances that conversion figure is substantial higher (say from wind power or hydro) it also doesn't take into account the declining energy returned on energy in standard oil production, especially with regard to tar sands or bio fuels. Just where do you want to start with the total calculation, especially as burning fuels in power stations is more efficient in any case, what are you trying to prove? Robthoburn (talk) 22:30, 24 March 2008 (UTC)
 * It is fair because 34% relates to the very difficult task of improving the efficiency of a small engine, not of generating power. The power equivalence is 11 kWh no matter how it is generated.  Same idea with fuel, it doesn't matter how the 115,000 BTU are created.  What matters is the fuel/energy efficiency of the transportation system or vehicle and that's what this page is about.  Ephdot (talk) 22:36, 24 March 2008 (UTC)

Still a strange comparison, I dispute it's helpful with rail systems powered by hydro/nuclear like France/Switzerland or even hybrid cars.Also ICEs idle, electric motors do not, so there are savings there. Maybe a cost comparison is more helpful, prices of electricity/gasoline. Robthoburn (talk) 22:46, 24 March 2008 (UTC)


 * You want to use ""36.6 kw/h" per GGE. That's pretty strange too.  We are not comparing cost.  We are comparing fuel efficiency. If diesel engines of trains are already quite a bit more than 34% efficient, you have a case for making the 11 kWh number higher.  This would set the bar even higher for automobile engines of course.  Don't forget to account for Diesel's higher BTU content before making a comparison.  Ephdot (talk) 22:57, 24 March 2008 (UTC)

I accept that there is a power generation element to electric. What I don't accept is one size fits all in the way you want to convert, because fuel efficiency could be substantially increased in certain circumstances. Therefore what you are presenting as fact is untrue.

I don't see the comparison with the actual efficiency of the machine, it should only be what fuel in/use as a user of that machine.

While the BTU argument is helpful, I think it should be seen on context if a conversion is made. Robthoburn (talk) 23:19, 24 March 2008 (UTC)


 * What I present as fact is that the average heat engine is about 34% percent efficient at converting the heat content of fuel to work/power. In fact, this reference to the book "Handbook of Transportation Engineering

By Myer Kutz" states that the thermal efficiency of the [locomotive] diesel engine is about 33%.
 * http://books.google.ca/books?id=fMZlnmS5YDMC&pg=PT589&lpg=PT589&dq=diesel+%22thermal+efficiency%22+locomotive&source=web&ots=nfEhSACtJk&sig=dyOtW8jpDJtZAjqSc_Dh983EIYg&hl=en#PPT589,M1
 * Why only the fuel in? In that case, how do you compare kWh to gasoline for example?  We've been here before...
 * The "kWh/100 km" is explicit and so is the Litre equivalent. MPGe is a defined comparison method explained in the caveats section as a "simple tool for comparison".  Can we agree that 3X mpg (36 kWh/GGE) for electric is excessive and misleading at least?  Ephdot (talk) 23:32, 24 March 2008 (UTC)

36Kw/h is correct as a direct comparison end user, but clearly there are other inputs. And this is the problem. I don't agree with your methodology because it's one size fits all, that could be used against some very responsible schemes because it can exaggerate the energy end cost.

For non motorised transport, energy inputs should be looked at into food. For example it has been argued that excess meat eating creates a lot of pollution, in order to have energy to walk. Possibly more than some motorised transport.

Nuclear: Uranium mining -> Yellow cake processing -> Nuclear fuel -> Steam heating and generation -> Turbine -> Electric Energy -> Transmission losses (usually around 4%) -> Electrical Energy

Hydro: Water potential energy -> Turbine -> Electric Energy -> Transmission losses (usually around 4%) -> Electrical Energy -

Wind: Wind kinetic energy -> Turbine -> Electric Energy -> Transmission losses (usually around 4%) -> Electrical Energy

Tidal: Gravity affects tides -> -> Electric Energy -> Transmission losses (usually around 4%) -> Electrical Energy

Gasoline: Oil drilling -> Transport to refinery -> Oil refining -> Transport/Pipeline to Oil depot -> Transport to distribution point -> Gasoline energy

Coal: Coal mining -> Coal transport to power station -> Steam heating and generation -> Turbine -> Electric Energy -> Transmission losses (usually around 4%) -> Electrical Energy

Biofuel: Various inputs including water, fertiliser and seed for crop and maintenance of crop by vehicles -> Harvest crop -> Refine crop -> Transport/Pipeline to Oil depot -> Transport to distribution point -> Gasoline energy

1)	You want to start actually with the comparison actually putting the gasoline in the tank, when there are other inputs 2)	Losses are very variable in reality with electrical power. 3)	Efficiency within the vehicle is irrelevant; it should be the energy inputs to that vehicle and at the most the inputs to getting that energy to the vehicle. Besides electric vehicles are far more efficient. 90% compared to around 30% 4)	No methodology for hybrids or regen – which can save up to 20% of energy. 5)	What data should be input, say construction of power stations or roads to get the gasoline to market? Should headline power generation be included, comparison with centralised grid/distributed grid. 6)     The energy requirements of a transportation system would also include vehicle life costs (for which trains/planes last longer than buses and substantially longer that private cars), energy cost of infrastructure, including indirect infrastructure such as the requirement to take long trips to airports by other methods and maintenance.

On and environmental level any comparison would have to take account of 8)     Energy sources 9)      induced demand from more transport 10)    Role of efficiency and cutting costs which induces more demand (Jevon's Paradox) 11)     Planning 12)    Congestion 13)     Flexibility and inducing more demand 14)    Speed and inducing more demand 15)     Food miles comparison for freight and relative localised inputs.

I do understand the problem, what I want to avoid is oversimplifying. IF that is done, the methodology and inputs must be spelt out.

Robthoburn (talk) 00:35, 25 March 2008 (UTC)


 * you just puked a life cycle cost argument (again) at a fuel efficiency problem. Heat engines are about 34% efficient which translates to 11 kWh which can be used to fairly compare the efficiency of different transportation.  I guess we can't even agree that 3X mpg (33 kWh/GGE) for electric is excessive and misleading.  Seems obvious to me.  Ephdot (talk) 00:44, 25 March 2008 (UTC)

What I object to is comparing a 34% efficient vehicle with a 90% efficient one. Its disingenuous. It doesn't fairly compare at all because you would need less energy input into the latter to drive it one mile. A tramway powered by hydro in Switzlerland doesn't involve inefficient heat engines, so why involve them?

I can buy into the argument that losses should be included in order to drive that electric vehicle, which vary a lot, but there are losses in liquid fuels as well. They don't magically appear at the car/bus whatever!

Robthoburn (talk) 01:01, 25 March 2008 (UTC)


 * Vehicles aren't 34% efficient, only the heat engine that converts fossil fuel to energy is 34% efficient. This is but one component of many factors that affect vehicle efficiency.  Drag coef., rolling resistance, weight, patronage etc...  are some of the others.  An electric vehicle with a drag coefficient of 1.5 is not "90% efficient".
 * What "losses" are you talking about? Setting an equivalence of 11 kWh per US gallon of gasoline isn't a loss, it's a reality that only about 34% of fossil fuel energy can be used.  You can think of a US gallon of gasoline as 11 kWh's worth of electricity.  No loss.  Ephdot (talk) 01:32, 25 March 2008 (UTC)

I’m fully aware of the various inefficiencies within vehicles and there is a lot more besides in the overall system but the only comparison required is how much energy to you need put in and how far that vehicle travels. For per passenger comparisons the load is considered. For example, if an electric trains needs 11kw/h to move 1 mile, then that's all that needs to be worried about, what happens internally is irrelevant - apart from how many people are on it! I can accept there are losses involving making that 11kw/h but they vary depending on the energy source.

Why are you constructing a case making electric vehicle look more inefficient that that are. We can accept they aren’t 90% overall, but strap an ICE to the same vehicle and it would be even LESS efficient and would need MORE energy at point of use to travel 1 mile.

11kw/h IS a loss - A direct conversion is 36kw/h! You are including losses for heat engines which are not involved with some vehicles. Robthoburn (talk) 01:59, 25 March 2008 (UTC)


 * So you are also 84.65.209.122. Who is we?
 * I'm constructing anything, you are. You are trying to make a case for converting the complete heat value of fuel into electricity - not possible (yet at least).
 * Really? That's exactly how Diesel-electric works and it's more efficient than a straight Diesel.
 * Which vehicles? Ephdot (talk) 02:12, 25 March 2008 (UTC)

Address the point, where are heat engines involved with a hydro powered tramway in Switzerland?

If you concede that losses must be included for power generation to get energy from say a nearby hydro plant to a tramway (and Im not saying they shouldn't be added and never did) you must also allow losses in getting other fuel sources to the point of use.

Robthoburn (talk) 02:21, 25 March 2008 (UTC)


 * So you are also 84.65.209.122. Who is we?
 * What's your point about the tramway? It's clean hydro power, and...
 * Back to the life cycle cost thing again. Who are you?  Are you sharing an account?  What kind of games are you playing?  I've had enough of these games.  Ephdot (talk) 02:43, 25 March 2008 (UTC)

The point about the tramway is it doesn't involve heat engines, so how can I be constructing a case for 'for converting the complete heat value of fuel into electricity'?

You, meanwhile, want to construct a case for adding inefficiencies into a system which don't (always) exist. - Which is just as bad as adding a 'theoretical load' which you saw fit to delete? You said, you want facts, I'm dealing with facts. But we'll deal with all the facts, not just the ones that suit you.

And yes life costs are important, especially when someone wants to use selective facts and build a case against something. Robthoburn (talk) 02:58, 25 March 2008 (UTC)

Nuclear, coal fired, and gas fired electrical power stations are classified by their thermal energy input, usually expressed in MegaWatts (thermal). Most grid electricity in most regions is produced some combination of these plants. The average thermal efficiency of these plants is around 33%, meaning that it takes three Joules of thermal energy to produce one Joule (or Watt-second) of electricity. Why not convert all fuel economies to distance per thermal Joule, and state the assumption that one is using electricity from some region in the US electrical grid, circa some year? This was done in the following reference: http://www.bentham-open.org/pages/content.php?TOEFJ/2008/00000001/00000001/11TOEFJ.SGM Ergophile (talk) 05:11, 15 June 2008 (UTC)


 * Because some regions use hydroelectricity which is a non thermal supply. Besides, that would be OR.- (User) WolfKeeper (Talk) 18:50, 15 June 2008 (UTC)

WolfKeeper, what is OR?

Granted, there are cases where the immediate source of electrical energy is non-thermal, but in today's world that is the exception. 90% of the electricity generated in the US comes directly from thermal sources. See: http://en.wikipedia.org/wiki/Image:Sources_of_electricity_in_the_USA_2006.png

Here is another reason to specify thermal energy units. Even hydroelectricity is produced from thermal energy that becomes kinetic energy. It is just more difficlut to quantify the conversion ratio. The sun is a thermal energy source. Electrical energy is a more highly organized form of energy than the chemical energy available in a gallon of gasoline. By comparing thermal energy liberated by combustion of a fuel in air to thermal energy required to produce electrical energy, a measure of the relative quality of these two forms of energy may be obtained. Rather than say that a gallon of gasoline is worth less, it is more accurate to say that 134 MJ (or 37 kWhr) of electricity is worth more. How much more can approximated by measuring the quantity of thermal energy we humans may use to produce electrical energy. This could be a nationwide or worldwide average.

IMO, use of MPGe to specify electric vehicle fuel economy is hopelessly confusing. Energy units need only be specified with a subscript "e" or "t" to discriminate electrical from thermal. This is standard procedure in powerplant engineering. Ergophile (talk) 04:43, 16 June 2008 (UTC)

Standardization
Let's use MPGe as a basis with the SI equivalent L/100km in parentheses. Ephdot (talk) 20:20, 20 March 2008 (UTC)

Let's use the coal equivalent in electricity production - 11 kWh per Gallon equivalent. Why? Coal is a very polluting and common electricity production method. The skeptics of electricity use will be satisfied and the clean energy proponents can point to displaced coal or gasoline equivalents as motivation. Ephdot (talk) 20:20, 20 March 2008 (UTC)

Disputed this is an agreed method of measuring fuel use since normally 1 gallon US gasoline = 36.6 kw/h not 11 kw/h. —Preceding unsigned comment added by Robthoburn (talk • contribs) 19:54, 24 March 2008 (UTC)

Let's add a note to every electric MPGe for an explanation of energy use conversion and replace with actual electricity generation figures and line loss numbers. Ephdot (talk) 20:20, 20 March 2008 (UTC)


 * Since 1 gallon equivalent is 11 kWh of electricity, we convert X MPGe = X/11 miles per kWh.
 * Since we have 3.79 L in a US gallon, we have 2.9 kWh/L. So Y L/100 km = Y/2.9 kWh/100km.

Standardisation is nonsensical for coal generation. Some countries such as France has very little coal generation. —Preceding unsigned comment added by Robthoburn (talk • contribs) 14:38, 24 March 2008 (UTC)
 * Exactly, power generation methods vary too widely. Using 11 kWh/GGE makes it an easy way to compare using your own power generation numbers.  Ephdot (talk) 15:03, 24 March 2008 (UTC)

Line loss is only nonsensical as it varies as is also not part of the transport infrastructure. It is a weakness in the power supply system, eg distributed v centralised and the method of generation/distances/voltage. —Preceding unsigned comment added by Robthoburn (talk • contribs) 14:38, 24 March 2008 (UTC)
 * Without power lines, electric trains go nowhere. Ephdot (talk) 15:03, 24 March 2008 (UTC)

Likewise without liquid fuels, other methods of transport go nowhere. —Preceding unsigned comment added by Robthoburn (talk • contribs) 15:21, 24 March 2008 (UTC)

More to the point, you would need the full losses of bringing liquid fuels to market. —Preceding unsigned comment added by Robthoburn (talk • contribs) 14:38, 24 March 2008 (UTC)
 * A diesel-electric train uses an on-board generator connected to an electric drive system. An electric train takes the generator out, replaces it with a more efficient external generator, suffers some line loss, enjoys some weight advantage and works quite nicely.  No problem figuring out how much diesel would be used in this case.  It gets tricky when power is generated from a mix of other sources like coal, natural gas, Nuclear, Solar etc...  Since there is no fuel used in Solar energy, you can't compare actual sources.  You either need equivalent sources for comparison or you leave it at kWh/mile and NEVER try to convert to mpg.  Since many source references make conversions, some in nonsensical ways, it is useful to use a single method for comparison. MPGe is this method.  Ephdot (talk) 15:03, 24 March 2008 (UTC)


 * SI should be primary. MPGe and GGE are not understood by the general public especially outside of the US.  MPGe is actually a rather confusing unit: it looks like a distance per volume unit but it's really distance per energy. It doesn't correctly convert to L/100 km. The template uses Ephdot's template which makes conversions based on assumptions of loss.  Is this not bordering on original research. It's time to iron this article out. J IM ptalk·cont 05:53, 21 August 2009 (UTC)

Still more messy values and units
The international reference for values and units are clearly laid out in ISO 31-0 which, for our American friends, has been transposed into an ANSI standard. Preference is given to SI units or derived SI units. ISO and subsidiary organisations mandate such in their documents but allow other units in parentheses after the SI unit. For example, it would be correct to say 12 kg (26.46 lb). Note the mandatory space between the value and the unit: this is to avoid ambiguity between l and 1 and between O and 0, which may occur with many typefaces. For example, is 23lm 23 lumens or 231 metres? Furthermore, there is a strict rule about capitalising abbreviated units: capitals are reserved for where the unit is derived from a person's name or a place name. All others must be lower case. I conclude that it would therefore seem wise to use l/100 km (not L and not 100km) or even l.100 km-1 with the option of mpg (which should really be mi/g! as mpg could be metre.petagrams in SI-speak!) in parentheses after, specifying mpgUS or mpgUK, for example.--213.7.112.173 (talk) 15:56, 24 March 2008 (UTC)
 * I used L/100 km to match the rest of wikipedia. You may change ALL references if you like starting here Litre...  Ephdot (talk)  —Preceding comment was added at 16:07, 24 March 2008 (UTC)
 * I like the US subscript. Much more compact and less distracting. Ephdot (talk) 17:28, 24 March 2008 (UTC)
 * Both "l" & "L" are acceptable. What's "mi/g", miles per gram? Miles per gallon is not metric so need not be abbreviated in the style of the metric system.  I agree with giving preference to SI. J IM ptalk·cont 05:59, 21 August 2009 (UTC)
 * I would agree that L (capital el) for "litres" is a perfectly acceptable variation and unambiguous; and also that it causes confusion to abbreviate non-SI units in pseudo-SI style.Peter Barber (talk) 14:20, 19 September 2009 (UTC)

I would also put in a plea for standardising on SI units first - as per WP:MOS! - this is not a US-specific article. I really appreciate the effort which has gone into collating the data and developing this article, given its breadth and topicality, but the units are a mess. I struggle to digest it myself and I'm a scientist who's good at maths. I am in the UK, where supposedly we still love imperial units, but my education, both state and private, from thirty years ago, was more or less exclusively in metric, as was the education of everyone else since the 70s. On the usage of "miles per gallon equivalent": it seems to be asking for trouble, in an encyclopaedia of international readership, to use a unit only used in one country (miles per US gallon-equivalent), with the same name as a different, and obsolescent, unit in another country, and even worse, a unit based on an attempt to express values for non-internal-combustion prime movers (including legs) as an equivalent volume of a particular hydrocarbon fuel. I wasn't even aware until last year that the USA had a different definition of the gallon (and fluid ounce, and pint, etc.) from the UK, so I doubt many people in the rest of the world who don't use gallons at all will find this distinction easy to make. Litres per hundred kilometres (L/100 km) is unambiguously defined, and an internationally accepted official unit of liquid fuel consumption (including for vehicle fuel consumption in the UK). If energy consumption rates of widely differing prime movers need to be compared, it should be in kilowatt-hours or megajoules per (passenger-) kilometre, for the same reasons. Peter Barber (talk) 14:20, 19 September 2009 (UTC)

70% reduction in aircraft fuel consumption?
Under the Aircraft subheading, the following is stated: "Between 1960 and 2000 there was a 70% overall fuel efficiency gain. [17]" The very first paragraph of the summary of the report to which note 17 links states: "This report assesses how the fuel efficiency of commercial aircraft has developed since their introduction in the 1930s. Existing estimates, such as the oft-cited 70% improvement from the IPCC Special Report on Aviation and the Global Atmosphere, ignore the record of the pre-jet era. Based on bottom-up (micro) and top-down (macro) analyses of aircraft fuel efficiency, it can be concluded that the last piston-powered aircraft were as fuel-efficient as the current average jet. This result was obtained by comparing several large piston-engined aircraft with both old and new jet airliners and was confirmed by the macro analysis, which reveals a sharp increase in fuel consumption per seat-kilometre as piston-engined aircraft were replaced by jet- engined. The last piston-powered airliners were at least twice as fuel-efficient as the first jet-powered aircraft." Even without this, the very statement "a 70% fuel efficiency gain" is problematic. Does this mean that fuel consumption dropped by 70% of the initial rate (i.e. dropped to 30% of the initial), or does it mean that an aircraft now travels 70% further on the same amount of fuel (i.e. a 41.2% reduction in rate of fuel use)? I have seen both meanings used interchangeably, despite being completely different concepts. This is another problem that arises with the miles per gallon unit: it is a reciprocal of fuel use, and therefore not distributive, i.e. several sequential increases of x mpg do not lead to several equal reductions in fuel use, which makes comparisons of various improvements more difficult. At the very least, the quoted sentence should be altered, and probably deleted as likely to mislead. Thoughts? Peter Barber (talk) 13:02, 23 September 2009 (UTC)