Like the rest of the carbon accounting/footprinting industry, we’ve always used DEFRA’s published figure for the carbon intensity of electricity of 0.43 kgCO2 per kWh. DEFRA has now released figures showing that the actual carbon intensity of the UK’s electricity is about 0.53 kgCO2 per kWh. Some members of the Association for Environmentally Conscious Building think the figure should be even higher at about 1.0 kgCO2 per kWh.

Why is this an issue? Well if you are comparing, say a Ground Source Heat Pump to a gas fired condensing boiler, and if the Heat Pump is working at a co-efficient of performance of 3.5 (that’s 3.5 units of heat out for each unit of electricity in), then, under the new DEFRA figures, the GSHP will produce 70% of the carbon dioxide of the boiler, whereas under the old figures it would be just 58%. That’s quite a difference and could seriously affect a decision on whether to spend the extra cash required for the Heat Pump.

So why did we use 0.43? Well, we always try to source our data from reliable, published and transparent sources and this was the industry accepted figure. DEFRA is going to continue to use 0.43 until 2010, but from now on we’ll be using 0.53 and be keeping an eye on the debate over 1.0.