Work out fuel consumption of boiler instantly with clear inputs, formula shown and shareable results.
Fuel demand starts from required output divided by efficiency, which gives the heat that must be released in the furnace. Dividing by the fuel heating value converts energy into physical units: cubic feet for natural gas at about 1030 BTU/ft³, gallons for oil at about 138,500 BTU/gal.
Fuel rate
units/h = output / (efficiency x heating value per unit)
units/h = output / (efficiency x heating value per unit). Fuel demand starts from required output divided by efficiency, which gives the heat that must be released in the furnace.
Match it to the efficiency figure. Efficiency quoted on gross calorific value must be paired with gross heating value, otherwise the fuel figure is out by 8-10 percent for natural gas.
This calculator takes 4 inputs: Boiler output, Boiler efficiency, Fuel heating value, Firing hours per day. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.