The renewable heating market has lots of facts and figures available. One of the key political issues is “does it save carbon?” and “is the carbon reduction worthwhile?”.

What are the key things to look for?

With heat pumps there are a number of issues on calculations.

Where does electricity come from? This can be produced in any number of ways e.g. Power station and coal, Wind or Solar PV. The accepted way is to use an average. The accepted government average is 0.53 kg per kWh. This is based on Gas (0.5 kg per kWh) and Coal (possibly greater than 1kg per kWh) at the moment with a view to this being reduced to 0.43kg per kWh as a figure that can be used for projections.

What is the COP figure? The term coefficient of performance (COP) is used to describe the ratio of useful heat movement to work input. This could range from 8:1 to 2:1 for instance. The figure changes depending on the machine (Manufacturer, Air source (ASHP) or ground source (GSHP)) or the job that it asked to do (ie heating to a higher temperature will decrease the cop figure). This means that you could gain 8 units of heat (kw) for using 1 unit of electricity or 2 units of heat for 1 unit of electricity.

The heat pump does not produce carbon emissions on site, but does use electricity.

If your installation is going to use a ratio of 6:1 then the carbon emissions would be 0.53/6 = 0.09kg per kWh.

If your installation were going to use a ratio of 3:1 then the carbon emissions would be 0.53/3 = 0.18kg per kWh.

As a reference oil is 0.265kg per kWh and gas is 0.194 per kWh

Clearly as electricity is produced in a more environmental way then the carbon savings from heat pumps improve. Both examples above show some carbon savings against both gas and oil.

If you want to find out more about “green” electricity