MWh(25) meaning in oil and gas

High Calorific Value at 25 degree Celcius or HCV 25°C

quantity of heat, expressed in kWh, which would be generated by the complete combustion in air of one m3(n) of dry Gas at a constant pressure equal to 1.01325 bar, with the Gas and air being at an initial temperature of 0 (zero) degrees Celsius, all the combustion products being brought down to 25 (twenty five) degrees Celsius, the water vapor formed during combustion being returned to a liquid state, and all other products being in a gaseous state. (from grt.arteredeguyenne.com)