Draft:Electric Sub Meters

Electric Sub meters
Electric subsidiary meters or prepaid meters are utility submeters used to track the energy (electrical) consumption of tenants and are primarily used by landlords or property owners. Electric sub meters are connected or installed downstream of the main meter on the property and are not used as a replacement but are only fitted in the area requiring its own electricity e.g. a tenant’s room. The main meter is the one supplied by the council or municipality and it always remains on the property.

Electrical sub meters assist property owners by providing the information needed to improve energy efficiency or to allocate electricity invoices equitably to tenants. They can also identify wasteful usage and faulty equipment. Without electrical sub meters, property owners would have to divide the usage measured by municipality or council and this is not always a fair representation of each tenant's consumption and may lead to disputes.

How do Electric Sub Meters Work?
Once electric sub meters are installed by electricians in the tenant’s area, tenants have to purchase electricity codes or pins that they will input into the sub meter in order to have power on - the amount becomes electricity credit that gets reflected on the sub meter.

The code/ pin they purchase is generated at a specific tariff rate provided by the landlord and once the meter credit runs low, the tenant must top-up or their electricity will be suspended. Tenant’s can then control their consumption and costs as they determine the amount they use.

Electric submeters are used for six basic reasons: as a tool for energy management by owners, to allocate electrical usage costs among tenants, as a tool to better the installation of energy conservation equipment, to allocate electrical usage costs among diffrent departments, to analyze power quality issues and to detect maintenance issues. The primary users of submetering equipment are office and residential buildings as well as industrial and institutional facilities.

Benefits of Electric Sub Meters
Electric Sub meters or prepaid meters improve the management for commercial or residential properties and this benefits the owners as well as tenants in the following ways:


 * Reduces administrative tasks and saves time as electricity is paid for upfront and there are no collection hassles.
 * Improves tenant and owner engagement as there is transparency in the consumption and payment.
 * Easy top ups for tenants due to the improved technology and different payment options which tend to be online.
 * Easier monthly accounting for property owners and managers
 * Saving money for both parties as electric submeters halves electricity bills due to tenants being wary of what they use and can control it.
 * Improves property valuation by raising a property's net income and through the capitalization rate being applied.
 * The electric sub meters are secure and unique to each tenant.

Electric Sub Meters Applications
Electric sub meters can be used by properties or instances in which electricity consumption payments need to be recovered or collected. These include apartment buildings, student accommodation, commercial offices, warehouses, houses with multiple occupations (HMOs), block of flats, mobile home communities, events where electricity must be metered, etc.

There are different rules and regulations for sub-metering depending on the country and this can affect the kind of properties that electric sub meters are installed in.

Types of Electric Sub meters
There are different types of electric sub meters or prepaid meters and each is designed for specific environments, situations or requirements. These are usually the integrated meter and the split meter and they are all keypad based sub meters.

Integrated sub meters
Integrated sub meters have the keypad directly on the meter and are usually compact. They are installed inside the tenant’s unit. These can be single-phase or three-phase sub meters.

The integrated single-phase (ISP) meter is a two wire, keypad based sub meter in a property. Tenant’s interaction with the meter and access to information i.e. when the credit is low, energy used etc. is accessible using the LCD display and keypad.

The integrated three-phase (ITP) meter is a four wire, 100 Amp per phase keypad sub meter in a compact property. It has a diagnostic indicator, assists technicians to authenticate the installation and inspect faults. Tenants can access information using the LCD and keypad.

Split sub meters
Split sub meters have keypads that are separated from the meter. The meter can be secured in a different location to minimise bypassing and tampering. The tenant only has access to the keypad, which communicates with the meter, for recharging purposes. These are installed differently i.e. the split single-phase (SSP) sub meter communicates with the keypad through wires while the split single-phase STS does so through power line communication (PLC).

The split single phase (SSP) sub meter has an energy management unit (EMU) and a customer interface unit (CIU). It is a compact, two wire keypad electric sub meter. The CIU is the tenant’s only interface with the meter and is installed away from the EMU, which is connected through communication wires. The EMU has all the critical metering functionality, operates separately and cannot be tampered with on the CIU.

The split single phase STS sub meter operates like the SSP but is connected through power line communication (PLC) using existing wires in the property. It is usually installed in a secure box or pole-mounted outside a property for easy inspection.

Technological improvements
Most technological advancements in electrical sub meters have been in their communication capabilities, including wireless, ethernet and satellite communications. Electric sub meters can now regularly transmit data over a facility’s existing ethernet infrastructure, allowing facility managers to have real-time access to the information without installing a separate network and to take advantage of web technology to remotely monitor and collect information regarding electricity usage. Microprocessors used by the second generation of smart meters allows for more efficient collection of electrical usage information resulting in more accurate information.