Will I save money with a ground source heat pump?

Working out how much heat you require from your system is important when determining whether a ground source heat pump is right for your needs. It can be tricky to work this out, due to the vastly different efficiency of gas or oil heating systems in comparison, but you can get a good idea by looking at your current usage and the efficiency of the system. Most gas boilers, for example, are 85 – 92% efficient, meaning for every £1 it costs you to use, you receive £0.85 – £0.92 worth of heat.

First: Looking at how much energy you consume, you can do the calculation below to work out your demand.

[energy usage] x [boiler efficiency] = heat demand

To put this into a real life example, a household that uses 10,000 kWh per year and has a gas boiler with 92% efficiency:

10,000 x 0.92 = 9,200 kWh heat demand.

Next: What can a ground source heat pump produce?

Usually, ground source heat pumps are 350% – 450% efficient. This means that for every £1 of energy they use, they produce £3.50 – £4.50 worth of heat. To phrase it differently, a ground source heat pump provides 3.5 – 4.5 units of heat for every unit of energy it uses. To work out how much energy you would be using to produce the same amount of heat you currently have, you can do the below calculation:

[heat demand] ÷ [GSHP efficiency in units] = energy requirement

To put this into a real life example, a ground source heat pump with an efficiency of 350% (producing 3.5 units of heat per unit of energy used). In the example household, this would look like:

9,200 ÷ 3.5 = 2,628 kWh energy requirement

Keep this number in mind while moving on to the next calculation.

With your above calculations written down, you can move on to looking at energy costs for electricity. This differs for each tariff and changes throughout the year, with current prices higher than ever. Ground source heat pumps use electricity to run, and so any energy costs associated with having one in your property will be based only on electricity prices, though remember that due to their efficiency they don’t use nearly as much energy as gas or oil to produce your heat.

Looking at your energy requirement number, do the following calculation to work out how much electricity you may need to use with a ground source heat pump.

[energy requirement] x [unit price of electricity] = cost of running a ground source heat pump

Using the real world example household, and the current average unit cost of electricity (as of March 2024 – OFGEM source) of £0.29 per kWh:

2,628 x 0.29 = £762.12 per year

The example household will have energy costs of £762.12 per year to run a ground source heat pump and keep their heat output to the same level.

Now that you have your calculation, you can work out your current costs and compare. Don’t forget these considerations when looking at your current costs:

• The unit cost may be different, so when working out future costs it’s a good idea to take your yearly usage and calculate the cost using current averages or your tariff for the following year if you know it.
• The gas standing charge, if you’re using gas currently. Make sure to include the standing charge in your current costs for a more accurate comparison. If you’re using electric only already, no need to add this as it won’t change.
• Your boiler or ground source heat pump efficiency will possibly be different to the above calculations, it is worth finding out both to get an accurate estimate of costs.

If you would like to discuss your options or would like an expert to help you make these calculations, our team is available. We provide estimates to all customers as part of our quoting process.