Ground Source Heat Pumps: The Complete UK Guide

What a Ground Source Heat Pump Actually Is

A few feet down, the ground in the UK sits at about 8C to 12C all year, even when there's frost on the grass (Kensa's figures). A ground source heat pump taps that. It pumps a water and antifreeze mix (installers call it brine) through a long loop of pipe buried in your garden, the brine soaks up that low-grade warmth, and the heat pump concentrates it into useful heat for your radiators, underfloor heating and hot water.

It's the same refrigeration cycle your fridge uses, just running in reverse and at a much bigger scale. Nothing burns, there's no flue, and once the ground is reinstated there's little to see outside. The whole machine lives indoors, usually in a utility room or garage; the Energy Saving Trust compares the indoor unit to an American-style fridge.

The reason it beats air source on efficiency is simple: it's pulling heat from ground at around 10C rather than from freezing winter air. The colder the air, the harder an air source pump works. Ground source doesn't have that problem, so it runs steadier and more efficiently exactly when you need heat most.

Horizontal Trenches vs Vertical Boreholes

There are two ways to get the loop into the ground, and which one you can have usually comes down to how much garden you've got.

Trench and borehole sizes are the Energy Saving Trust's; the depth depends on your heat demand and the geology.

Trenches are cheaper because a digger is cheaper than a drilling rig. Boreholes cost more but barely touch your garden, and the Energy Saving Trust notes they can be more efficient because deeper ground is warmer. If you've got the space, trenches are the cheaper option on our estimates. If you haven't, a borehole is what makes ground source possible at all.

What It Costs, and Why Quotes Vary So Much

When you compare prices, make sure each one is for the whole installed system, ground loop included, not the heat pump unit alone. Here's what the published numbers say:

• The Energy Saving Trust puts a typical install at "around £15,000" with the loop in trenches, and "considerably more" with a borehole. What households actually paid under the Boiler Upgrade Scheme runs higher, so the table above uses DESNZ's figures. DESNZ doesn't separate trench systems from boreholes, so we've assumed trenches sit in the cheaper half of its range and boreholes in the dearer half.
• The government's own figures (DESNZ Boiler Upgrade Scheme statistics) put the middle half of ground source installs at £18,100 to £42,100 in April to June 2026, median £27,200, and the 2025/26 median at £26,200. That's from a few hundred installs a year, so treat it as rough, and it covers everything from a small trench system to boreholes on big houses.
• The ground collector is the big variable. Trenching or drilling is where ground source gets expensive, and it depends entirely on your soil, access and how deep the borehole has to go. On our estimates a trench system is £18,000 to £27,000 installed and a borehole £27,000 to £42,000.

Knock off the £7,500 grant and the middle half of real installs comes to £10,600 to £34,600. There's also 0% VAT on the whole job, including the groundworks, until 31 March 2027 (it goes up to 5% after that), which is already in those prices. Your three quotes are the real answer.

Use the calculator to get a figure for your own home, and to answer the question that actually matters: whether the ground loop is worth paying for versus a cheaper air source pump.

Running Costs and Efficiency

This is where ground source shines. On our assumptions a well-designed system runs at a SCOP of about 4.0 across the year, against 3.5 for a typical air source pump. That needs a low-temperature system: underfloor heating or generously sized radiators, so a design flow temperature around 35 to 45C. Push the flow temperature to 55C and it drops like any other heat pump. At the 1 October to 31 December 2026 price cap, that means heat at about 6.6p per kWh against 8.9p from a 90% gas boiler and 7.5p from an air source pump. For a typical three-bed on our model, that's about £630 to £680 a year on a standard tariff.

Two things move that number a lot:

• Your tariff. Because the hot water cylinder lets it make hot water in the cheap hours, ground source pairs well with a heat pump electricity tariff (Cosy Octopus, EDF Heat Pump Tracker and similar, compared in our heat pump tariff guide). On our blended estimate, shifting heating into cheap windows cuts the electricity rate by about a quarter against the 26.3p standard rate. There's more in our heat pump running costs guide.
• Your radiators. A heat pump delivers water at around 35 to 55C, not the 70 to 80C a gas boiler uses (British Gas's figures). Undersized radiators will leave rooms cool. Many homes need a few rads upsizing, or underfloor heating, to get the best out of it. See do I need new radiators for a heat pump.

Grants: the £7,500 Boiler Upgrade Scheme and the Rest

In England and Wales, the Boiler Upgrade Scheme (BUS) gives you £7,500 off a ground source heat pump, the same as air source, and gov.uk says it covers water source pumps and shared ground loops too. The scheme is installer-led: your MCS-certified installer applies and takes the grant straight off your quote, so you never handle the cash. A few rules worth knowing:

• One grant per property, and you must be replacing a fossil fuel system (gov.uk lists oil, gas, electric and LPG). You can't get a grant to replace a low carbon heating system.
• An extra £1,500 until March 2027 if your home is heated by oil or LPG and has no mains gas connection. It applies to ground source as well as air source.
• There's no grant for a hybrid (gas boiler plus heat pump) setup.
• Ground source gets a longer voucher than air source, which matters when the groundworks slip. Under regulation 15(2) of the BUS Regulations 2022, a ground source voucher expires six months after it's issued (air source gets three), and no ground source voucher can run past 31 March 2030. Agree the dates with your installer before they apply.

There's no need to rush a decision this big: the scheme runs to 2030. The Boiler Upgrade Scheme (Amendment) Regulations 2026 (SI 2026/390) replaced the old 2028 end date, so Ofgem can issue vouchers until 31 December 2029, and the Warm Homes Plan funds it with £2.7 billion to 2030.

Elsewhere in the UK, Scotland offers up to £7,500 in grant plus an interest-free loan of up to £7,500 through Home Energy Scotland (with a £1,500 rural uplift on top). Wales has the Nest scheme for eligible households. Northern Ireland has no general heat pump grant, though its NISEP schemes fit free heat pumps for some lower-income homeowners (household income under £28,000 single, £35,000 for a couple). Full detail is in our heat pump grants guide.

Is Ground Source Actually Worth It? An Honest Verdict

For a typical home, no, and we'd rather tell you that now than after you've spent the money. Ground source runs a bit cheaper than air source, but not by enough to claw back its much higher install cost before the kit wears out. On a typical three-bed, our model puts the running cost saving over air source at about £80 to £90 a year, while the DESNZ 2025/26 medians put ground source about £13,200 dearer to fit. The maths rarely works on bills alone.

So pick ground source for the reasons it's genuinely better, not to save money:

• You've got the land. A big rural plot makes horizontal trenches affordable and easy.
• You're building or doing a deep retrofit. Digging is cheaper when the ground's already open and you're fitting underfloor heating anyway.
• You want silence. There's no outdoor fan unit, so it's effectively silent outside. That matters for tight gardens, holiday lets, or noise-sensitive neighbours.
• Air source can't cope or isn't allowed. A large, heat-hungry or listed property where you can't site an external unit is the classic ground source case.

Here's how ground source stacks up against the realistic alternatives. It's highlighted as the option you're weighing up. It wins on running cost, lifespan and quiet, while air source wins on the upfront bill for most homes:

If none of those describe you, get an air source pump and put the difference towards insulation. For a side-by-side breakdown, see air source vs ground source and our full heat pump costs guide.

Honest Pros and Cons

The genuine pros

• The most efficient system we cover: we'd expect a SCOP of 4.0 or more, ahead of air source and far ahead of a gas boiler
• Very low running costs, especially on a heat pump electricity tariff
• Near silent outside, with no outdoor fan unit for you or your neighbours to hear
• Built to last: Kensa says its heat pumps last up to 25 years and the ground array 100 years or more, against 10 to 15 for a gas boiler
• Holds its efficiency far better than air source in a cold snap, because the ground stays at around 8C to 12C
• The same £7,500 Boiler Upgrade Scheme grant and 0% VAT (until 31 March 2027) as air source
• Nothing outdoors to look at, find space for, or watch rust

The genuine cons

• Far higher upfront cost (the middle half of installs were £18,100 to £42,100), and the premium over air source rarely pays back on bills alone
• You need a large garden for trenches, or the budget for a borehole
• The groundworks are disruptive and weather-dependent
• Like any heat pump, it wants a well-insulated home and larger radiators or underfloor heating to run at its best
• Not realistic for most terraces or flats, unless a whole building shares a ground loop
• Fewer installers fit ground source: in the MCS installer data behind our directory (October 2026), 669 firms were certified for ground source against 2,230 for air source, so quotes can take longer to gather

The Install: What Actually Happens, and How Long Things Last

Expect a survey first, including a proper heat-loss calculation and a look at your ground and access. Boreholes usually need a specialist ground survey too, the Energy Saving Trust says. Then the groundworks: digging for trenches, or a borehole rig on site. Indoor fitting (heat pump, cylinder, controls, any radiator changes) usually takes a few more days. On our rough estimate, most jobs run over one to two weeks once work starts.

In England, a new closed-loop system installed since 2 October 2023 also has to meet the Environment Agency's conditions for low-risk sites or its position statement for homes, or have a permit. Your installer or driller should check which applies to your plot.

Once it's in, it's low-maintenance. The buried ground loop has no moving parts, and Kensa expects the array to last 100 years or more. The heat pump unit itself just needs a routine annual check, and there's nothing to service outdoors and nothing to rust in the rain. Our heat pump servicing guide has Kensa's warranty conditions, which include an annual system check.

What to Look For in a Ground Source Quote

Ground source is a big, infrequent purchase, and quote quality varies a lot. Get at least three from MCS-certified installers, and check each one names these specifics:

• A proper heat-loss survey (MCS methodology), not a rule-of-thumb kW figure plucked from your floor area.
• The ground array design: trench length and layout, or the number and depth of boreholes, with the calculation behind it.
• MCS certification for the install (you need it for the £7,500 grant), plus a borehole contractor with proper drilling credentials.
• Design flow temperature (lower is better; under 45C is excellent) and the expected SCOP at your design conditions.
• Warranties spelled out: the ground loop should be guaranteed for decades, and the heat pump unit for several years.
• Garden reinstatement: who makes good the lawn or driveway after trenching, and whether that's in the price.
• Environment Agency position: which exemption, position statement or permit the system will be installed under.
• Electrical supply: whether it runs on your existing single-phase supply or needs an upgrade, and the cost if so.

And a few things worth questioning if they show up on the quote:

• An oversized unit or more borehole than the heat-loss calc justifies, which just piles on cost.
• A buffer tank added "to be safe" with no clear hydraulic reason.
• Replacing every radiator when a handful of upgrades would do.