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Offgrid

Discover more about a renewable electricity generation system that won't require a mains connection

Isolated homes with no mains electricity supply either have to make do without electricity, or generate their own. For these houses, a renewable electricity generation system - using wind, water or solar power to generate power - could be the answer.

Living with an off-grid system is never like living on the mains, but it can be cheaper than getting a mains connection, and is much cheaper and quieter than running a diesel generator.

Minimising power use

The first step in setting up an off-grid renewables system is to minimise your electricity use. This is important for all home renewables systems, but if you’re off the grid it's vital.

To reduce the electricity you need and therefore the size and capital cost of any renewable energy systems for electricity, tasks such as water and space heating can be done by using dedicated renewables such as biomass boilers, ground and air source heat pumps or solar water heating. Surplus wind and PV electricity can be used to complement these systems once appliance demand is met and your batteries are full.

Batteries 

The heart of most off-grid systems is the battery store. A bank of deep-cycle batteries will store electricity when it is generated and provide power for when it is needed. With proper controls and system design, a battery bank may last five years or more, but it will not last for ever, so you should budget to replace the batteries several times during the life of a system.

Most deep-cycle batteries are lead-acid batteries, like car batteries but with thick solid plates to cope with the deep charging cycle. Batteries with liquid acid in them require care, as they give off hydrogen gas when charging, and they may lose water over time, which will need replacing. More expensive AGM batteries do not contain liquid, and are much easier to look after.

Batteries can be charged by more than one generation technology: you might have an exposed site with a wind turbine, some photovoltaic panels to provide input during windless spells, and a diesel generator as backup and for running high-power appliances for short periods.

A hydro resource may be reliable enough for you to do without batteries or back-up generator, but this depends very much on the site (and on the needs of the household). 

Inverters

Electricity from the batteries can be used directly to run low-voltage lighting and perhaps other direct-current (DC) appliances. However, most systems include an inverter to produce mains voltage alternating current (AC), which can be used to run standard appliances.

The inverter may act as a battery charger, as well as looking after the batteries and controlling the system, or you may have several separate boxes for these different functions.

Feed-in Tariff payments

All renewable electricity generated by an eligible installation can receive payments under the Feed-in Tariff scheme. This is true for off-grid systems as well as on-grid ones – you will get the same generation tariff, though obviously you can’t get export payments.

To qualify for FIT payments, the installer and the generation equipment must be registered under the Microgeneration Certification Scheme. Off-grid systems are complicated, and it is important that they operate safely and effectively, without damaging the generators, batteries and household appliances. We would strongly recommend that you find an MCS installer who is experienced in off-grid installations, and that you ask them to design the complete system.

This content was developed by the Energy Saving Trust in partnership with the OCTES project, with funding from the Northern Periphery Programme (NPP) and the Scottish Government.

More information

Set up an off-grid renewable electricity system

Find out more at the Centre for Alternative Technology (CAT)

Visit CAT website

Based in Scotland?

Find out about support available through the Feed-in Tariffs scheme in Scotland.

Find out more