English: rated thermal input
Welsh: cyfradd y mewnbwn thermol
Subject: Amgylchedd
English definition: Defined for the purposes of other legislation as 'the rate at which fuel can be burned at the maximum continuous rating of the appliance multiplied by the net calorific value of the fuel and expressed as megawatts thermal'.
Welsh definition: e.e. cyfradd mewnbwn thermol o 20 MW