Over the last few years there has been a drive by the uk government to reduce our reliance on fossil fuels and reduce CO2 emmision in our homes.

Previous grant funding schemes such as the renewable heat incentive (RHI) for renewable technologies such as heat pumps and biomass boilers and now the newer Boiler Upgrade Scheme (BUS) incentivice homeowner to invest in these technologies by providing financial subsidies.

But with all this being said, will it actually improve the energy rating of a property and lower my energy bills?

Well it depends.

First we need to understand what metric the EPC uses to rate the property.

The metric it uses is the cost to provide heating, hot water and lighting in the home. So the lower the running costs, the better the EPC rating will be.

When you install a Heat Pump you will be changing from whatever fuel source you currently have be it gas, oil, lpg etc to electric.

How Efficient Are Heat Pumps?

Heat pumps, and we’re taking about air source heat pumps here, are between 250% to 380% efficient, depending on make and model.

This means for every 1Kw of energy the heat pump uses, it outputs between 2.5 to 3.8 kw of usable energy in the form of heat.

This is extremely efficient, compared to a good condensing gas boiler which is only 90% efficient at best.

However, that’s not the whole story. Unfortunately because of the cost of electricity, it will still cost more to heat and provide hot water to a home with a heat pump than it would with a gas boiler.

So if you’re changing from a gas boiler to a heat pump, it will definately lower your epc rating and increase your energy bills.

Ground source heat pumps are even more efficient at around 400%. It’s only at that level is it a comparible running cost equal to or better than gas. However, ground source heat pumps are significantly more expensive and will be a subject for another article.

Under the governments previous renewable heat incentive scheme, in their guidance document it said:

“Although the Domestic RHI scheme is for homes both on and off the gas grid, the latter are usually more expensive to heat and have higher carbon emissions. Those without mains gas have the most potential to save on fuel bills and decrease carbon emissions.“

So in their guidance note above, it’s saying in a roundabout way that installing a heat pump may not be the best option for everyone.

The main driver for government is to reduce CO2 emmisions. This a heat pump will definately do.

Why heat pumps are more suitable for newer properties

In the new building regulations which came into force from June 2022, there is a new CO2 emmisions target for each new home and that target can only be met by installing either a heat pump or solar photovoltaics.

But with new homes being super insulated and air tight, the running costs are very low and any cost differentials between using gas and electric for a heat pump are a lot smaller.

However, this is not always the case for a lot of the existing housing stock.

So the main answer to will a heat pump lower my energy bills and improve my epc rating is really dependant on the fuel source you are moving from.

We will look at some examples below. Here we take a deep dive into the EPC software to show you some comparisons using different fuel sources.

Examples and comparisons of moving from different fuel sources to a Heat Pump

Before we look at the examples, there are 2 important terms we need to understand about heat pumps they are:

• Coeffiency of Performance (COP)
• Seasonal Performance Factor (SPF)

What is Coeffiency of Performance (COP)?

Coefficient of Performance (COP) is a number that shows how much heat a heat pump can produce for each unit of electricity it uses.

Imagine you have a heat pump in your home that is used to heat the air in the winter. If the heat pump uses 100 units of electricity to produce 300 units of heat, the COP would be 3 (300 heat units / 100 electricity units = 3). This means that for every unit of electricity used, the heat pump is able to produce 3 units of heat. So, the higher the COP, the more efficient the heat pump is.

Seasonal Efficiency Performance (SFP)

Heat Pumps Seasonal Efficiency Performance, or SFP, is a measure of how efficiently a heat pump can heat a home over the course of an entire heating season.

It is typically expressed as a ratio or percentage, with a higher number indicating more efficiency.

The SFP takes into account factors such as the outdoor temperature, the heat pump’s performance at different temperatures, and the amount of time the heat pump runs.

A heat pump with a high SFP will be able to heat a home efficiently even when the outdoor temperature is very low.

For an Air Source Heat Pump a typical SPF is 2.8 and for a Ground Source Heat Pump a typical SPF is 4.0.

As Air Source Heat Pumps are by far the most common, our examples will be using an SPF of 2.8.

Comparison Examples Of Moving From Different Heating Sources

In the following epc ratings and running costs comparisons, we are going to show the epc rating and the running costs moving from the following fuel sources:

• mains gas boiler to a heat pump
• oil boiler to a heat pump
• storage heaters to a heat pump
• LPG boiler to a heat pump

All the examples, if there is a boiler, will be moving away from a high efficiency condensing boiler.

I should also mention, these are actual comparisons entered into the actual EPC software.

There are many discussions on the internet whether the EPC methodology accurately reflects the impact of heat pumps.

That discussion is for another article. What we are demonstrating here is the actual output from the EPC whether we agree with it or not. 

I will be using 2 properties of different thermal values. The only changes that will be made to the properties in the examples below will be the heating system.