How to Calculate a Burner's Gas Consumption
The formula for a burner's gas consumption at a given power, with an example from the manufacturer's manual: 500 kW is about 52 Nm³/h of natural gas. Units and calorific value.
Gas consumption follows from the burner's power and the fuel's calorific value. One formula is enough, but you need to watch the units.
Formula
Gas consumption [Nm³/h] = power [kW] × 860 ÷ calorific value Hu [kcal/Nm³]. The number 860 is the conversion factor: 1 kW equals 860 kcal/h.
Example from the manufacturer's manual
A 500 kW burner, natural gas with a calorific value of 8,250 kcal/Nm³:
- Q = 500 × 860 = 430,000 kcal/h
- V = 430,000 ÷ 8,250 = 52.1 Nm³/h
What to watch out for
- The calorific value of gas depends on its type and composition. For natural gas, the manufacturer uses 8,250 kcal/Nm³ in the tables, and 22,500 kcal/Nm³ for LPG. The actual value is given by your gas supplier.
- Burner power versus boiler power. The burner supplies more energy than the boiler releases, because the boiler's efficiency is below 100%. Burner power is boiler power divided by efficiency.
- Nm³ versus m³. A normal cubic metre refers to standard conditions; gas from your installation may be at a different pressure and temperature.
For quick calculations, use our calculator — it handles natural gas, LPG and light fuel oil.
Send us the data from the boiler or furnace nameplate — we will size the burner.
Power, fuel, combustion chamber pressure. We reply within 48 hours, with no obligation.