Boilers are an important part of an EPC. How you heat your home, (whether that be with an ultra-efficient modern boiler, or a 40 year old floor-standing boiler), the EPC rating will be heavily influenced by it. That said, is changing your heating a good way to improve the rating, or should you focus on other options to get the rating up? With EPC ratings becoming ever more crucial for rental purposes, this can be an important decision.

Boiler Efficiency

The oldest boilers installed in households are around 65% efficient, usually floor mounted and open-flued. The most efficient boilers are usually wall-mounted condensing boilers, and can be up to 90% efficient. With that in mind, lets take a pretty average older property with an old boiler currently installed.

I have assumed that the heating controls are exactly the same and that hot water is drawn from the boiler, so only the boiler is changed. Before replacing, the house is F36 rated. After replacing the boiler, the rating leaps to E54. That is a fairly dramatic change, which now makes it marketable for rental under the new legislation.

Heating Controls

In the above example, we have not included any heating controls in the calculating software at all. If we take the property with a new boiler and add in some basic heating controls – that is a programmer thermostat and thermostatic valves – you will boost the rating by 3 points to D57. Add a slightly more complex zonal control system and you will get to a D60 rating, that is a whole 6-point increase just for having good heating controls.

Of course, most properties will have some sort of heating control to begin with, so it rarely makes more than a few points difference for the average property.

What about electric heating?

Electric heating is really inefficient, even if you are using it in an off-grid property. Let us take the same house we have been using and make it off grid. As a baseline, we will add simple electric convector heaters with an immersion heater, which gets us to a rating of G8. The property is identical to the one above, just off-grid with electric heating, so you can see how badly the rating is affected by electric heating.

Lets now switch the property to storage heating on a dual or Economy 7 meter. The hot water cylinder now runs off a dual immersion system. The rating has shifted up to E39, just enough to pull it over that rentable level. But is there anything that performs better than storage heaters in terms of EPC rating?

Heat Pumps

Installing a heat pump can sometimes mean a better performance on the EPC, but for this property there is actually no difference between this and storage heaters. We get an E39 if we install a heat pump with programmer, room stat, and hot water running off the heat pump, as well as a switch to a single meter.

If a heat pump is installed in a well insulated property, you might suspect that the rating will show a bigger difference between storage heaters and heat pumps; but actually we found that storage heaters generally are a point or two better in this situation – so heat pumps are rarely the answer to improve your rating it would seem. The exception might be with ground source heat pumps, or an ultra efficient air source heat pump, where a several point improvement can usually be made. Even better is a solar thermal system, which can really help the performance of a heat pump. In our scenario, a basic solar thermal system improved the rating by 6 points when tied to a heat pump, whereas adding solar thermal to a storage heater and immersion system will only provide a 2-point boost in this example.

Using Heating to Improve your EPC rating

If the heating system in your property is a basic electric system, or you have an old boiler, upgrading could make quite a bit of difference to the EPC rating. As always however, every property is different, and we wholeheartedly recommend a full recommendations report from one of our assessors before you look to make any of these improvements. This way you can be absolutely sure what is going to be the most cost-effective way to improve that rating!