55% of your energy bills is spent on heating.
According to the Energy Saving Trust: “Heating accounts for about 55% of what you spend in a year on energy bills, so an efficient boiler makes a big difference.” The biggest reason for modern combi boiler efficiency is down to condensing boiler technology.
Modern condensing boilers are normally 90-94% efficient. Boilers that are more than 15 years old can be as little as 60% efficient. What does boiler efficiency mean? A boiler’s ‘energy efficiency’ is the percentage of the total energy used by the boiler to supply useful heating to your home. For a modern boiler with 95% efficiency, 95% of the energy used by the boiler goes to heating the home, only 5% is lost through the flue. For a very old boiler with 60% efficiency, only 60% of the energy used by the boiler goes to heating the home, a whole 40% is lost through the flue to the atmosphere.
As a good rule of thumb for non-condensing boilers assume:
- Over 25 years old: 60% efficient
- 20 years old: 70% efficient
- 15 years old 80% efficient
- 10+ years old 85% efficient
Average Annual Energy Costs for different types of Boilers:
| Type of Boiler | Efficiency | Semi-Detached | Detached | Flat |
|---|---|---|---|---|
| Modern Condensing Boiler | 90%-95% | £720 | £1150 | £500 |
| Non-Condensing Boiler | 75%-78% | £850 | £1310 | £700 |
| Old Back Boiler (Light Weight) | 60%-65% | £1020 | £1450 | £800 |
| Old Back Boiler (Heavy Weight) | 50%-55% | £1260 | £1780 | £850 |