Condensing boilers explained
A condensing boiler makes better use of the heat that it generates from burning fuels such as gas or oil. In a conventional boiler some of this heat is wasted because the boiler releases very hot waste gases from its flue.
A condensing boiler uses some of the heat from these waste gases to heat water returning from your central heating system, so it requires less heat from the burner. This makes your condensing boiler more efficient.
The efficiency of a boiler is normally expressed as a percentage – some new condensing boilers can be up to 92% efficient compared to new non-condensing ones that are around 78% efficient, and older boilers that are only 55 to 65% efficient.
Quick facts about condensing boilers
They produce a visible plume of vapour when they are operating, so the flue terminal needs to be sited carefully to avoid the steam creating a nuisance.
They produce an acidic liquid that must be plumbed into a suitable drain.To comply with building regulations in England, Wales and Scotland, new or replacement boilers should be rated as Sedbuk band A or B, ie more than 86% efficient.
The Sedbuk boiler efficiency database lists all of the boilers in production, their efficiencies and estimated running costs in examples of typical houses.
These calculations were made when gas cost just 1.63 pence per kWh.
With current gas prices of two to five times more than that, it’s clear that the more gas you use, the more you’ll save now and in the future by going for the most efficient boiler you can afford.