With the ability to keep energy costs low and also contribute a sustainable element to self-build projects, ground source heat pumps have always been a popular choice with self-builders.

A key question though has always been “what’s the payback”.  With the recent launch of the new Domestic Renewable Heat Incentive (RHI) however, there has never been a better time for self-builders to consider solutions such as Ground Source Heat Pumps in their project.


Launched in April this year and aimed at promoting large scale uptake of renewable heating technologies, the RHI quite simply guarantees to pay an attractive income for all the renewable heat generated for a period of 7 years.  Coupled with the energy cost savings made against the likely alternative fossil fuel heating system, self-builders can now expect a typical ground source heat pump to realistically produce a “payback” in around 5 years or less and provide a tidy profit in return.

While the scheme covers a range of renewable heat technologies, ground source heat pumps offer a number of distinct benefits – the least visually intrusive of the options available, exempt from additional planning permission restrictions, the most efficient, quiet in operation and above all, delivers the lowest annual energy costs for heating and domestic hot water.

For ground source heat pumps, the RHI pays an income of 18.8p/kWh for the “renewable” proportion of the energy needed to provide heat and hot water to your home.  How much that will mean to you will depend on a number of factors, but ultimately comes down to the calculated energy consumption of your self-build (as confirmed by your building Energy Performance Certificate) and the “efficiency” of your system.

Ideal for well insulated, low energy buildings, ground source heat pumps work most efficiently with underfloor heating, as heat can be distributed across a large surface area at a low water temperature.  This suits ground source heat pumps well, allowing them to work to their optimum efficiency, a fact that will be represented by both lower running costs and a higher RHI payment – as a higher proportion of the heat will be coming from a “renewable source”.

That isn’t to say that heat pumps can’t work effectively or the RHI won’t stack up where radiators are installed or the heat pump is used to produce domestic hot water. Indeed, for practical reasons, heat pumps almost always provide hot water as well as heating and many designs employ underfloor heating downstairs and radiators on upper floors.  The slightly higher water temperatures required simply mean that RHI payments will be affected slightly.

To help calculate what the RHI could do for your self-build, UK market leading manufacturer Kensa has produced a handy online tool to help you find out a little more about the costs and how much you could make and save by installing a ground source heat pump.  It will also tell you what size system you are likely to need and how much land area you are likely to require. See https://www.kensaheatpumps.com/grants-incentives/domestic-rhi/calculator-tool/

Ultimately, the outcome for any self-builder is likely to be compelling.  For example, for a modest 4 bed detached self-build:

 Compared with GasCompared with Oil
Annual fuel cost saving£350£800
Annual RHI income£2000£2000
Total benefit over 7 years£16,450£19,600
Typical installation cost£13,000£13,000
Payback5.5 years4.5 years
Share Button