Determining boiler efficiency

The boiler efficiency should be based on the Higher Heating Value (HHV) or the Gross Calorific Value (GCV). Where the information related to the efficiency of the boiler is only available in Lower Heating Value (LHV) or Net Calorific Value (NCV), it will need to converted using the following formula:

HHV = LHV x 0.9

GCV = NCV x 0.9