Boiler Efficiency

Boiler efficiency is the ratio of useful heat delivered to the energy in the fuel burned. Losses come mainly from flue gas, radiation/convection from hot surfaces, and blowdown. Improving it — better combustion control, economisers, insulation — cuts fuel use proportionally.

A boiler running at 80% efficiency wastes one-fifth of its fuel. The largest loss is usually the hot flue gas leaving the stack, addressed with economisers and air preheaters. Radiation and convection losses from the boiler shell, valves and pipework are reduced with insulation, and blowdown losses with heat recovery. Combustion analysers and controls keep the air-fuel ratio optimal.

Related terms

Economiser · Boiler Blowdown · Waste Heat Recovery · Superheat · Heat Loss

Related guides

Where this applies

Commissioning a new boiler · Changing over a boiler feedwater treatment programme · Adopting condensate recovery · Establishing a steam-trap survey programme · Switching a boiler from fossil fuel to biomass · Adopting reverse-osmosis water pre-treatment · Retrofitting a boiler economiser · Adding flue-gas oxygen trim control