To ask the Secretary of State for Energy and Climate Change what estimate he has made of the likely effect on UK carbon emissions of replacing all UK household boilers with combined heat and power boilers. (242482)

The Government have been funding trials of combined heat and power systems through the Carbon Trust. The results of these trials suggest that, with currently available technology, micro-CHP boilers would only provide cost-effective reductions in carbon emissions in up to 20 per cent. of homes—generally larger dwellings with above average heat demand.

The replacement of all UK household boilers with domestic micro-CHP boilers is unlikely to prove cost-effective. But, as an illustration, if 5 million units were installed in the most appropriate homes, CO₂ savings would be around 1.5 MtCO₂ per year, at today’s carbon intensity of grid electricity.

A longer term influence comes from the predicted decrease in the carbon intensity of grid electricity, due to changes in the mix of power generation. This will reduce the CO₂ savings per unit, and hence also the cost-effectiveness, although technology developments and changing costs will also affect this.