Mark Headshot (2)

Mark Howard, project manager at Regen, discusses how shared ground arrays could unlock a larger market for ground source heat pumps, whilst reducing peak winter electricity demand.

The housing challenge

A report published by the Environmental Audit Committee this week[1] highlighted that the task of retrofitting our housing stock to meet net zero is “colossal”, and that the absence of urgent and long-term policy leaves housing “at risk of letting the rest of the economy down on decarbonisation”.

Having spent a number of years in industry supplying and installing renewable energy systems, I would agree – delivering lower carbon solutions in the face of an economy that doesn’t place value on the negative carbon impact of the goods and services it delivers is a challenge. Couple this with the need to make changes in 28 million homes, and you have a serious challenge.

However, I have also seen the benefits that a warmer, low carbon home can bring; beyond the kWh and kg CO2e there is nothing like the satisfaction (for all involved) of making someone’s home more comfortable. If we can reduce some of the barriers to the uptake of low carbon heat, there is a huge opportunity to bring more than just carbon savings, such as improved comfort, a smarter energy system, and new and engaging jobs in a growing sector.

This blog provides an overview of our recently published paper that looks at taking a utility-based approach to ground arrays for heat pumps as one approach to reducing these barriers. The overall findings are summarised in the graphic below.

Rethinking heat inforgraphic

To find out more about these conclusions read on, or read the full paper.

Heat pumps as part of the solution

With the heat pump industry expecting to double installation numbers in 2021[2] and a recent government commitment to drive installations to 600,000 a year by 2028[3], we look set to see heat pumps established as a key heating technology in the UK.

Alongside this anticipated increase, government noted in the Energy White Paper2 that “we need to electrify heat in buildings in a way which reduces the need for additional generation and network capacity”. As ground source heat pumps (GSHPs) typically offer greater annual and peak day efficiency[4], ‘Rethinking heat’ explores whether there is a greater scope for use of GSHPs to meet these ambitions.

Our analysis suggests that, in a future where heat pumps are the predominant heat source, a modest increase in the proportion that are GSHPs could mean a 10% reduction in the demand that heat puts on the electricity network at winter peak. The indicative modelling suggests a reduction in peak electricity demand that ranges from less than 1 GW to as much as 7 GW, depending on the modelling assumptions adopted.

Bringing down barriers

The key to unlocking this significant potential is reducing one of the barriers to GSHP installation – the cost and practicalities of installing a ground array which can represent a high proportion of upfront costs. Most homeowners would not expect to be responsible for coordinating and fully funding the design and installation of the water, gas, electricity, or broadband infrastructure that serves their properties, however this is the case with a GSHP ground array, infrastructure that would be expected to last 50 years or more. This is where shared ground arrays come in – a shared array can be owned and financed completely separately from the heat pumps in peoples’ homes, drastically reducing the deployment cost to each householder and providing a long-term revenue stream to the array owner equivalent to the gas standing charge[5].

Not only would this approach reduce one of the key barriers to GSHP adoption, it would also increase the size of the potential market by ~11 million dwellings by offering flats and terraced houses the potential to connect, rather than being constrained by a shortage of land in which to install a private ground array.

Regen analysis suggests that replacing the up-front cost of the ground array with a standing charge, in combination with appliance price reductions (highlighted in chapter 7 of the paper), would bring the typical 30-year total cost of ASHP and GSHP ownership at least to parity. This would better enable the most appropriate type of heat pump solution to be installed in any given instance, opening up opportunities where either heat pump solution may have proven challenging.

There is a nascent market for this approach, estimated to have been delivered in ~4,000 homes in the last two years, supported by the Renewable Heat Incentive (RHI). With RHI support about to come to an end, it is important that this approach is supported further as one potentially significant route to decarbonising our homes.


Our key recommendations are that, in the forthcoming Heat and Buildings strategy, the government:

  • Commissions analysis of the system to provide a better evidence base on the impacts of different mixes of ASHPs and GSHPs, with a particular focus on: real world heat pump performance; spatial analysis of temperatures and heat demand to understand the significance of peak demand both for National Grid and DNOs; potential for flexibility, to mitigate a proportion of peak day demand.
  • Uses the current ‘Electrification of heat demonstration project’ to better understand the comparative network impacts of ground source, air source and shared loop heat pump systems.
  • Changes the environmental levies on the electricity bill into a carbon levy on electricity, gas and oil bills, based on their carbon impacts.
  • Ensures the update of the Smart Systems and Flexibility plan incentivises domestic customers to switch their electricity use to off peak times where possible.
  • Supports the financing and deployment of shared ground arrays as a new utility.
  • Provides confidence in the scaling up of demand for GSHPs so that UK companies can invest in the opportunities for manufacturing and installation.
  • Encourages local authorities and regional heat planners to prioritise opportunities for ground source and shared loop heat pump solutions.

A footnote: what about energy efficiency and other low carbon heat solutions?

Regen is involved in work across the energy system, with a mission focus on decarbonisation rather than specific technologies to achieve this aim.

It is without doubt that improved fabric efficiency is key to decarbonising our building stock, as discussed in our ‘decarbonisation of heat’ paper, something that we have first-hand experience of from projects such as ZEBCat,  which demonstrated whole house retrofit. Not only does improved fabric reduce the scale of demand and improve appliance efficiency, it is also key in eliminating fuel poverty and excess winter mortality in the UK.

Some 86% of homes in GB are heated by burning fossil gas, a further 10% are heated with direct electric heating, with most of the rest heated by non-networked fossil fuels such as oil or LPG. Low carbon heating currently serves only 1% of homes[6]. Given that heating buildings currently contributes 17% of UK greenhouse gas emissions[7], heating our homes by burning a fossil fuel will not be possible in a net zero world, and that 1% needs to shift to 100% in the next 29 years.

Whilst there are deliberations over the practicality, cost and scale of infrastructure required to deliver hydrogen and biomethane as a ‘drop in’ alternative to fossil gas[8], the immediately available solution at present is the heat pump. A discussion of Regen’s on-going research and analysis of the emerging low carbon hydrogen sector can be found in our recent ‘building the hydrogen value chain’ paper.

About the ‘Rethinking heat’ paper

‘Rethinking heat’ is a thought provoking discussion paper that challenges policymakers to apply whole system thinking to ensure that increasing the deployment of heat pumps delivers value for consumers and the overall energy system.

Kensa Heat Pumps Logo 370x150

As with previous insight papers, Regen has partnered with leading organisations that are willing to provide sponsorship. This discussion paper has been kindly sponsored by Kensa Group Ltd. All views and opinions expressed in the paper are Regen’s, unless otherwise indicated, and have been taken independently of the paper sponsor.


[1] Energy Efficiency of Existing Homes Fourth Report of Session 2019–21, House of Commons Environmental Audit Committee, 2021

[2] Heating and Ventilation Review, March 2020

[3] Energy White Paper, BEIS, Dec 2020

[4] Technical Feasibility of Electric Heating in Off-Gas Grid Dwellings, Delta EE, 2018

[5] Energy Infrastructure of the Future: Ground Source Heat Pumps, NIBE, 2020

[6] Data workbook, FES 2020, National grid ESO, 2020

[7] The sixth carbon budget – The UK’s path to Net Zero, Climate Change Committee, Dec 2020

[8] For example: Gas Goes Green, ENA, 2020 or Hydrogen: A decarbonisation route for heat in buildings?, LETI, 2021

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