Modern central heating condensing boilers are a lot more efficient than conventional non-condensing boilers. Non-condensing boilers waste between 30% to 50% of heat, as a result of combustion gasses escaping into the flue. However, a condensing combi boiler, in contrast, can be up to 99% efficient. 

​They can heat water more efficiently, meaning they use less gas or oil to do the same job. This saves energy and will save you money. In fact, if your boiler is over 10 years old, then it’s probably worth investing in a new one. In most cases the savings you make from a more efficient boiler over the years will likely pay for the outlay. Building regulations stipulate that if you are replacing an old boiler, the new appliance must be A-rated for energy efficiency. This means it must be at least 88% efficient (most new boilers score over 90%).

​In a typical semi-detached property that uses mains gas for heating you can reduce your heating bills by around £300 per year if you upgrade from an old G-rated boiler (less than 70% efficient) to a new A-rated condensing boiler with full heating controls (e.g. timer/programmer, room thermostat and thermostatic radiator valves). The savings are even greater for larger properties and for heating systems that run on oil which is more expensive than gas.

​The costs for replacing a boiler will vary, but a straightforward gas combi boiler replacement, including thermostatic radiator valves (TRVs) will typically cost from around £1500 to £2500 depending on the make and model of boiler, the size of the boiler and the location of the boiler in the property.