asked the Secretary of State for Energy what increase in thermal efficiency of coal-fired power stations has been made during the last 10 year period; and what is the total increase since 1947.

I am advised by the CEGB that the thermal efficiency, calculated in terms of net calorific value, of its coal fired power stations was 21·77 per cent, in 1947, 30·41 per cent, in 1971–72, and 34·06 per cent, in 1981–82: an increase of 3·65 percentage points from 1971–72 to 1981–82 and 12·29 percentage points from 1947 to 1981–82.