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AC – alternating current. This is the form in which electricity is delivered to our homes from the national grid.

Anemometer – a gadget to measure how windy your site is, prior to investing in a wind turbine.

Coefficient of Performance (CoP) -  is the measure of how many units of heat are generated per unit of electricity used.

DC – direct current. The type of electricity produced by batteries, solar panels and wind turbines.

Feed-in tariff – a minimum amount that anyone exporting electricity to the grid will be paid for each unit exported. A feed-in tariff is due to be introduced in the UK from April 2010.

Inverter – used to convert direct current (DC) electricity to alternating current (AC), so that it can power domestic appliances or be exported to the grid.

kWh – kilowatt hour is a unit used to measure energy. Electricity bills are charged in kilowatt hours, and it is the unit used to measure the energy generated by wind turbines or photovoltaic solar panels.

kWh/year - kilowatt hour per year. This can be used in terms of heat output, or the amount of energy needed to heat a house. For example, my solar thermal system is predicted to generate 2,517kWh of heat per year. The Department of Energy and Climate Change (DECC) calculates that the average household requires 3,742 kWh/year of energy to heat its hot water.

kWp – kilowatt peak is the measure of how much power a photovoltaic system produces from the sun under test conditions. It measures the power produced under 1kW per m2 of light. The more efficient the system, the smaller the area of panels needed.

Low carbon energy– this term refers to technologies which minimise the amount of carbon (or greenhouse gas) emitted into the atmosphere. At a domestic level it includes air and ground source heat pumps and combined heat and power. In national terms it includes nuclear power or the yet to be developed concept of carbon capture and storage – both of which continue to be controversial.

Microgeneration – is the generation of heat or power by renewable or low carbon means, by individuals, businesses or communities for their own use.

Miscanthus – also known as elephant grass, miscanthus is one of the front runners in the search for a commercially viable biomass crop in the UK and Europe. It is originally from China, but has a high yield when grown in the UK.

Renewable energy – energy generated from sustainable natural resources, such as sun, wind, water and geothermal heat. This includes biogas and biomass, hydroelectricity, solar heat and electricity, geothermal energy, wind, wave and tidal power.

Retro-fit - refers to products that are installed to an existing house, rather than as part of a new build. It tends to be more expensive to retro-fit, as systems such as plumbing might have to be changed.

ROC – or Renewables Obligation Certificates are designed to incentivise the large energy companies to invest in renewable energy. They are also paid to microgenerators who receive two for each megawatt hour of electricity generated.

U-value - indicates how well a part of the building (ie roof, window, door, wall) keeps the heat inside the building. It measures the heat flow through those components. The higher the figure, the higher the heat loss. It is measured in terms of how many watts (W) of thermal energy is transported through a component of 1 square meter (m2) at a temperature difference of 1 degree centigrade, ie W/m2.