Ground source heat pumps have higher electrical demands than air source — often requiring three-phase supplies, multiple circulation pump circuits, and careful earthing around the ground loop. This guide covers everything an electrician needs to know.
Free for 7 days · No charge until day 8 · Cancel anytime · Used by 1,000+ UK electricians
Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
A domestic ground source heat pump usually needs a dedicated compressor circuit plus separate circuits for the ground-loop and heating circulation pumps, zone valves, the controller, and any buffer-tank immersion heater. Single-phase models run to roughly 10kW electrical input; larger units typically need a three-phase supply, which means a DNO application booked early in the project.
1,000+
UK electricians
“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”
Daniel Palmer — DP Electrical
Ground source heat pumps (GSHPs) extract heat from the ground via a buried loop of pipe and use a compressor to upgrade that heat to a temperature suitable for space heating and hot water. They are the most efficient heat pump type (with a COP of 3.5 to 5.0), but the installation cost is significantly higher than air source due to the ground loop (borehole or trench).
GSHPs are typically installed in larger properties with sufficient land for the ground loop — detached houses, rural properties, and new-build developments. The electrical installation is more complex than air source because of higher power demands, multiple circulation pumps, three-phase supply requirements, and the ground loop isolation considerations.
This guide covers the electrical supply requirements, three-phase considerations, circulation pump and zone valve wiring, buffer tank circuits, ground loop isolation, MCS certification, and the relevant BS 7671 regulations.
Every key change in the 2026 amendment on one page. AFDDs, TN-C-S protection, new schedule columns, model forms. Pinned on your van dash.
Ground source heat pumps have higher electrical demands than air source units because they are typically sized for larger properties. The electrical load includes:
| Load | Typical rating | Notes |
|---|---|---|
| Compressor | 3–8kW input | Main power consumer. Starting current 3–5× running current; soft-start reduces inrush on many units. |
| Ground-loop circulation pump | 100–500W | Pumps the water-glycol mixture through the buried loop. Rating scales with loop length. |
| Heating circulation pump | 50–200W | Distributes heated water to radiators or underfloor heating. |
| Immersion heater(s) | 3kW each | Backup heating in the buffer tank or cylinder. Some systems fit two (upper and lower). |
| Controller and ancillaries | 50–100W | Zone valves, outdoor sensor, room thermostats, and the control panel. |
Total electrical demand for a typical domestic GSHP installation is 5 to 12kW. Carry out a thorough maximum demand assessment to determine whether the existing supply can cope.
Three-phase supply is commonly needed for ground source heat pump installations. The key triggers for a three-phase upgrade are:
| Factor | Single-phase | Three-phase |
|---|---|---|
| Typical GSHP size | Up to ~10kW electrical input | 12kW and above (common) |
| Supply capacity | 60A or 80A — check spare headroom | ~3× capacity (e.g. 3×100A) |
| Starting current per phase | Higher — can cause voltage dips | Lower — load shared across phases |
| Long-run voltage drop | Higher current per conductor | Reduced current per conductor |
| DNO lead time | Usually existing supply | 8–16 weeks for an upgrade |
A three-phase supply upgrade requires a DNO application and typically takes 8 to 16 weeks. The cost is £1,500 to £3,000 depending on the distance from the existing supply point. Apply to the DNO immediately after the site survey — this is usually the critical path item that determines the overall project timeline.
The three-phase consumer unit (or distribution board) must be designed to balance the load across the three phases. The GSHP compressor takes the three-phase supply; single-phase circuits (immersion heaters, circulation pumps, lighting) are distributed across the phases.
A GSHP system has at least two circulation pumps — one for the ground loop and one for the heating distribution. Larger systems may have additional pumps for separate heating zones or a dedicated hot water cylinder pump.
A common site mistake is routing 230 V power cables alongside low-voltage signal cables (0–10 V pump speed, PWM control, room thermostat wiring, outdoor sensor). Electromagnetic interference from the power cables can cause erratic pump speeds, false thermostat readings, and nuisance controller faults. BS 7671 Reg 444.4.2 requires segregation, screening, or other mitigation measures where EMI could affect equipment operation. In practice: run power and signal cables in separate conduit or cable trunking, or maintain a minimum 50 mm separation. Where crossing is unavoidable, cross at 90°.
The GSHP controller manages heating zones, hot water production, and weather compensation. The electrical wiring for the controller and zone valves follows the same principles as air source heat pump installations, but GSHP systems often have more zones due to the larger property size.
A buffer tank is almost always required with a GSHP to prevent compressor short-cycling. The buffer tank stores thermal energy and decouples the heat pump output from the heating demand. Most buffer tanks include one or two immersion heater elements for backup heating.
Indicative only — always size every circuit to the manufacturer data and confirm with a cable sizing calculation against your install method, grouping, and run length.
| Circuit | Supply | Protection | Isolation |
|---|---|---|---|
| Compressor | 1-ph or 3-ph per model | Sized to manufacturer FLC/MCA | Local isolator at the unit |
| Immersion heater (3kW) | 230V single-phase | 16A or 20A, ~2.5mm² cable | Double-pole switch / FCU |
| Circulation pumps | 230V single-phase | Often fed from controller | Fused spur / controller isolation |
| Controller / ancillaries | 230V single-phase | Switched fused connection unit | Local FCU |
16 certificate types, 70+ calculators, RAMS, quoting, invoicing, AI agents, and 46+ training courses — from £6.99/mo.
Start free trial
The ground loop introduces a unique electrical safety consideration. The loop pipe is buried in direct contact with the earth, and the water-glycol mixture inside the loop is in thermal contact with the ground. While HDPE pipe is non-conductive, the metalwork of the heat pump (heat exchanger, compressor casing, manifold connections) is connected to the fluid circuit.
As with air source heat pumps, MCS certification is mandatory for the lead installer to access the Boiler Upgrade Scheme (BUS) grant. The grant provides up to £7,500 towards the cost of a GSHP installation.
The electrical installation must comply with BS 7671:2018+A4:2026. The same regulations that apply to air source heat pumps also apply to ground source, with additional considerations for the ground loop:
The work is notifiable under Part P of the Building Regulations. Notify through your competent person scheme or via Building Control.
Ground source heat pump installations are high-value projects. The electrical package alone is typically worth £1,000 to £2,500, and the overall project values are £20,000 to £35,000. Building relationships with MCS-certified GSHP installers provides a steady stream of well-paid work.
Indicative UK market guidance, not a quote — actual prices vary by region, access, and supply distance.
| Item | Indicative range |
|---|---|
| GSHP electrical package (circuits, pumps, controller) | £1,000–£2,500 |
| Three-phase supply upgrade (DNO + board) | £1,500–£3,000 |
| Whole GSHP project (loop, pump, distribution) | £20,000–£35,000 |
| Boiler Upgrade Scheme (BUS) grant | up to £7,500 off |
Size the compressor circuit, circulation pump circuits, and immersion heater circuits with the cable sizing calculator. Three-phase calculations included.
Price GSHP electrical work with Elec-Mate's quoting app. Compressor circuit, three-phase supply, circulation pumps, zone valves, immersion heaters — all itemised.
Complete the EIC for GSHP circuits on site. AI board scanning, voice test entry, and instant PDF export for the MCS documentation package.
Join 1,000+ UK electricians using Elec-Mate for cable sizing, professional quoting, and on-site EIC certification.
Try it free for 7 daysVerified reviews from the UK App Store.
Elec-Mate is my go to app for business and electrical work. It's feature rich without feeling cluttered. A true all in one app for quotes, certs, calculations, RAMS, EICRs, and more. I use it every day without fail, and it makes my workflow much smoother since I'm not jumping between apps anymore. The price-to-feature ratio is excellent. Any issues I've had, the developer responds within the hour and usually fixes them the same day. 100% recommend.
I've used the app and the web based version for a while now and it's well worth the investment. If you're an apprentice or experienced Spark give it a go, you won't be disappointed.
I've been using Elec-Mate for a while now, and honestly, it's one of the best apps I've ever downloaded. Every aspect of it feels thoughtfully designed, from the clean and intuitive interface to the powerful features that make everything so easy to manage. It's clear that a lot of care and attention went into building this app, and it shows in every detail.
Real feedback from real sparks
“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”
Daniel Palmer
Sole Trader · DP Electrical
“I've won two contracts this month because I could turn quotes around same-day with the AI cost engineer.”
Nathan Perry
Electrician · NP Electrical Services
“The study centre got me through my AM2. Mock exams and flashcards are brilliant.”
Jake Pizey
3rd Year Apprentice · Apprentice
Join 1,000+ UK electricians using Elec-Mate for cable sizing, professional quoting, and on-site EIC certificates for ground source heat pump installations. 7-day free trial, cancel anytime.
“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”
Daniel Palmer, DP Electrical
From £6.99/mo after trial — less than a coffee a week
We use cookies to improve the app and measure what works. Cookie Policy