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Best Off-Grid Solar System Choosing the best off-grid solar system is not easy as off-grid systems are many times more complicated than common grid-connected solar systems. In this article, we highlight some of the many considerations which must be taken into account and discuss the various off-grid system types available. We also explain why a good quality ‘inverter/charger’ is vital to building a reliable off-grid system. Finally, we will dive into the different brands available and determine which systems are best suited to different applications.

Many people believe off-grid solar systems can be easily put together. This may be true in the case of a small caravan or cabin, but in reality, larger off-grid systems used for homes and businesses need to be carefully designed by an experienced solar installer or system designer.

Solar and battery storage systems must be installed by an experienced licensed electrical professional. Modern large scale off-grid solar systems are typically high voltage and can generate and store huge amounts of energy which can result in damage, fire or serious injury if the installation does not meet all relevant regulations, standards and guidelines.

The 5 Main Parts Of An Off-Grid System Battery Inverter/charger or Multi-mode Inverter

Solar inverter (AC) or Solar charge controllers (DC)

Battery bank

Solar panels

Generator (Optional) Off-grid system types - AC or DC coupled Off-grid systems are built using either AC or DC coupled power sources. AC coupled generation sources include common solar inverters, wind turbines or backup generators (gen-sets), while DC coupled sources include MPPT solar charge controllers or micro-hydro systems.

Whether a system is AC or DC coupled is generally based on the size of the system. Most small-scale systems less than 5kW are DC coupled and use solar charge controllers. Larger off-grid systems can be either AC or DC coupled depending on the type of inverter/charger (multi-mode inverter) used, and the compatibility with different solar inverters (AC) or solar charge controllers (DC). Most modern multi-mode inverters can be both AC and DC coupled, which creates a very secure, flexible system with multiple charging options.

Small Off-Grid Solar Systems Most small-scale off-grid solar systems used on caravans, boats, small homes and cabins use solar charge controllers, also known as solar regulators, which are connected between the solar panel/s and battery. The job of the charge controller is to ensure the battery is charged correctly and more importantly, not overcharged. Most solar charge controllers also have load output terminals which are often used for simple DC lighting circuits. In small systems, simple battery inverters are used to provide AC power, and are available in many different sizes, from tiny 150W inverters up to 3000W or even higher. DC-coupled solar charge controllers have been around for decades and are available in two main types, PWM and MPPT. Read more about solar charge controllers here, plus how to size small scale off-grid solar systems correctly. More powerful MPPT Solar charge controllers up to 100A are used on larger scale off-grid solar power systems. These are a very efficient and reliable way of charging and managing high capacity lithium or lead-acid battery systems.

Key considerations when sizing off-grid solar systems Daily average energy consumption (kWh) - Summer and winter

Peak load (kW) - Maximum power drawn from appliances

Average continuous load (kW)

Solar exposure - Location, climate, orientation & shading

Backup power options - During poor weather or shutdown

With the above considerations in mind the key component of an off-grid power system is the main battery inverter/charger often referred to as a multi-mode inverter as they can usually operate in both off-grid or on-grid modes.

Battery Inverter/chargers In AC coupled off-grid systems, the battery inverter/charger is the heart and brains of the system. Its primary job is to supply ‘pure sine wave’ AC power, and it must be able to meet the power requirements of the appliances under all conditions. In addition, the inverter/charger regulates the battery charging and monitors energy flow from all other sources such as solar, wind, hydro or backup generators. Below is more detail about selecting the best inverter chargers. The battery inverter/charger should be adequately sized and designed to power appliances such as water pumps, fridge compressors and air-conditioning units which require very high surge (peak) power during startup. This is where many cheaper inverters can fail. If multiple appliances are running at the same time then the inverter must also be able to supply continuous power under all conditions including higher temperatures, so must be sized correctly to account for temperature de-rating. Again this is where cheaper (transformerless) inverters can often trip, especially during high summer temperatures.

Technical Guide Recommended for solar Professionals - See our Technical guide to selecting and sizing off-grid and energy storage systems.

Technical guide to off-grid solar energy storage - Consumption profile.jpg A solar professional should be able to put together what is known as a load table to help determine which type and size inverter is best suited to your individual needs. A detailed load table is also used to size the solar array, battery and backup generator. Off-Grid Battery Options Lead-Acid Until recently, traditional lead-acid deep cycle battery systems were the most common and reliable option for off-grid systems. Lead-acid batteries are a proven technology and can last up to 15 or more years if they are not held at elevated temperatures (above 40 degC), and are not regularly discharged too low. Lead-acid batteries require precise battery charging following a specific charge cycle plus temperature sensors to adjust voltage settings. Most well known off-grid inverter/chargers offer programmable charge voltage settings along with sensors to precisely charge under all conditions. Lead-acid deep cycle batteries are still widely used and offer several advantages over lithium. One of the most significant benefits of lead-acid batteries is unlike modern lithium batteries; the battery will not shut-down at a low voltage or low state of charge (SOC). This is important, especially in emergencies or when a backup generator fails. Lead-acid batteries can be discharged down to 0% state of charge if needed for backup, but it is not recommended as it can severely reduce the life of the battery.

Advantages Compatibility with most inverters.

Proven and trusted technology.

Safe, very low risk (sealed Gel/AGM).

Battery will not cutout at low SOC or low voltage**

Long life (if not over discharged)

Easily recycled.

Disadvantages Lower efficiency - around 80%

Low energy density - Very heavy

Usable capacity limited - Max 40% DoD on regular basis

Not modular - Fixed size once installed

Cannot sustain partial state of charge for long periods

High temperatures can drastically reduce battery life


 * Cutout voltage & SOC based on inverter settings and rate of discharge.

Lithium-Ion More recently lithium-ion battery systems have become extremely popular due to the high efficiency (92% to 98%), compact size, lightweight and scalability. In contrast, lead-acid battery banks have a fixed size or capacity whereas lithium systems do not suffer this limitation. This flexible sizing allows for additional capacity to be added at a later stage, which is a real bonus for both installers and customers alike.

Lithium batteries have a much higher energy density compared to lead-acid and are therefore lighter and more compact. A huge advantage of lithium is the ability to sustain a low state of charge (partial state of charge) for a prolonged amount of time without any negative effects such as sulfation which is a common problem with lead-acid batteries. Also, extremely high charge rates can be achieved using lithium with charging times up to 70% faster than lead-acid. Advantages Very high efficiency - Approx 97%

Very high energy density - Light weight and compact

High charge and discharge rates allowed

No degradation with partial state of charge

Modular and scalable systems

Safe and low risk (if charged correctly)

10 year warranty

Disadvantages Can shutdown at high temperatures (45+ degC)

Can shutdown at low temperatures (below 5 degC)

Can ‘trip off’ under continuous high surge loads.

Can be difficult to recycle at end of life.

May not function without a compatible inverter.

Best Battery For Off-Grid Systems Managed lithium Many lithium battery systems contain a BMS which requires a dedicated communication link to the inverter in order to operate. If the inverter isn’t compatible with the battery then they cannot function together and will not work. One of the biggest issues with this type of system is that if communication is lost or suffers interference then often the inverter or battery will shutdown to ensure the battery is not over charged or discharged. For example, the BYD B-Box Pro battery has been reported to shutdown when exposed to low temperatures below 5 degC.

The BYD B-Box Pro battery is a popular managed lithium battery used for grid-connected systems as they are compatible with a large range of hybrid and off-grid inverters including SMA and Selectronic, and Victron. However, some performance and operational issues have been noted with the BYD batteries, especially in low temperature locations. LG chem RESU 48V batteries are popular, but only for ‘small’ off-grid systems due to the limited continuous discharge rate of 5kW. For larger off-grid systems the LG chem rack mount battery system is a better larger capacity option.

Modular self-managed lithium LFP battery system from PowerPlus Energy. Modular self-managed lithium LFP battery system from PowerPlus Energy.

Self-managed lithium There are several self-managed lithium battery options available which contain a BMS but do not require a fixed communication in order to operate. Most self-managed batteries are very modular and are able to be scaled to create very large capacity battery banks (up to 500kWh). Popular brands include include Simpliphi, GenZ, Discover AES and Powerplus Energy. Much like managed batteries, the internal BMS is still used to manage charging, monitor the state of charge, temperature and cell voltages. Another advantage with this type of battery is they can be easily retrofitted and used to replace existing lead-acid battery banks, since they do not require any special communications or connections.

Best Battery For Off-Grid Solar In my direct experience and based on feedback from many professional off-grid installers, self-managed lithium batteries are the best and most reliable choice for off-grid systems. Managed lithium batteries can be problematic as they rely on communications which can trip off or become unstable, especially at low state of charge and low temperatures. Most self-managed lithium battery systems are generally high quality and do not suffer from communication issues. They are also modular, flexible and can be expanded to create larger capacity energy storage systems which are better suited for off-grid systems. Additional capacity can also be added at a later stage if required.

Best lithium off-grid battery options self-managed.jpg The recommended self-managed lithium (Lithium Ferro Phosphate) batteries from the leading battery manufacturers include Simpliphi, GenZ, Discover AES and PowerPlus Energy.

Lead-acid Batteries In certain applications high performance lead-acid batteries are still an excellent choice for off-grid systems. Lead-acid is a well proven and reliable technology which is compatible with virtually all off-grid inverters and solar charge controllers. Lead-acid systems can also be more reliable in some situations as the battery will not automatically shutdown in extreme temperatures. In addition, they can be easily recycled using existing recycling infrastructure.

The Heart Of An Off-Grid System - The Battery Inverter/Charger Modern off-grid solar systems use multi-mode inverters/chargers to manage batteries, solar, and back-up power sources such as a generator. The inverter/charger is the central energy management unit and can be either AC coupled with solar inverter/s, or DC coupled with solar charge controller/s, or both. Read more about AC and DC coupled systems here.

Early off-grid systems used basic battery inverters and were very simple in comparison as the battery charger was a separate unit. These simple inverters generally had low power rating below 2kW and thus were only capable of powering low energy appliances like lights, fans and small pumps.

Many modern multi-mode inverter/chargers are very powerful (up to 20kW) and are designed to run high consumption appliances like air-conditioners, large pumps, electric ovens and hot water systems, which require high continuous power or high startup ‘surge’ current. Naturally these powerful inverter/chargers are much more expensive than common grid-connected solar or small capacity hybrid energy storage systems and can cost anywhere from $1500 to $6000* depending on the rated power output. (* 48V inverter/chargers up to 8kW)

Best off-grid inverters - Multi-mode Inverters Here is our list of the leading off-grid inverters on the market based on reliability, service, continuous and peak (surge) power rating, energy management software, AC source control, flexibility and monitoring.