The main route by which insulation and energy efficient light bulbs are promoted to households is through the Carbon Emission Reduction Target. This is an obligation on energy suppliers to meet household carbon emission saving targets. The suppliers’ unit cost of purchase and the level of subsidy they employ is commercial in confidence. The Government estimate that the total unit cost of compact fluorescent lights (including administrative costs) is around £1.41, and for cavity wall insulation is around £455. There are a number of variables which impact the estimates for the level of subsidy suppliers employ, including whether the household is a priority group or non priority group customer and whether it is in social housing. For example, for cavity wall insulation in non social housing, the estimate for energy supplier subsidy is on average just under 100 per cent. for priority group households and just over 50 per cent. for non priority group households.