Heat pumps are brilliant technology, but they’re not a plug-and-play replacement for your gas boiler. Getting the installation right makes the difference between slashing your bills and ending up with a cold, expensive mistake. Here are the 7 things every UK homeowner should know before committing.
1. Insulation Comes First – Always
A heat pump in a poorly insulated home is like filling a bathtub with the plug out. Heat pumps produce heat at lower temperatures than gas boilers, so your home needs to retain that heat efficiently. Before spending £10,000+ on a heat pump, invest in loft insulation (£300–£600), cavity wall insulation (£500–£1,500), and draught-proofing (£100–£300). These improvements often pay for themselves within 2–3 years regardless of your heating system.
2. You Need a Proper Heat Loss Survey
This is non-negotiable. A heat loss survey (also called an MCS heat loss calculation) measures exactly how much heat your home loses through walls, windows, floors, and ventilation. It determines the correct heat pump size for your property. A good installer will do this as part of their survey – if they quote without one, walk away.
| What’s Measured | Why It Matters |
|---|---|
| Wall U-values | Determines heat loss through walls – the biggest factor |
| Window type & area | Single/double/triple glazing affects heat loss significantly |
| Floor insulation | Uninsulated solid floors can lose 10–15% of heat |
| Loft insulation depth | Should be 270mm+ for heat pump efficiency |
| Air tightness | Draughty homes need more heat – and bigger pumps |
| Room-by-room radiator sizing | Each radiator must deliver enough heat at lower flow temps |
3. Your Radiators Might Need Upgrading
Gas boilers push water at 60–75°C through your radiators. Heat pumps are most efficient at 35–45°C. At these lower temperatures, your existing radiators might not emit enough heat to keep rooms warm. Solutions include adding larger radiators in key rooms (£150–£300 each), adding underfloor heating where possible, or choosing a high-temperature heat pump (like the Vaillant aroTHERM plus at 75°C).
4. You’ll Need a Hot Water Cylinder
If you currently have a combi boiler (instant hot water, no tank), you’ll need to add a hot water cylinder when switching to a heat pump. Heat pumps heat water more slowly than gas, so they need a stored supply. Budget £500–£1,000 for a 200–300 litre cylinder including installation. You’ll also need the space for it – typically an airing cupboard or utility room.
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5. The £7,500 Grant Changes the Maths
The Boiler Upgrade Scheme (BUS) knocks £7,500 off the installed cost. Without it, heat pumps are hard to justify on cost alone. With it, they’re competitive with – or cheaper than – a new gas boiler over 15 years.
| Scenario | Typical Cost |
|---|---|
| Heat pump installed (before grant) | £10,000 – £15,000 |
| BUS grant | -£7,500 |
| Your cost | £2,500 – £7,500 |
| New gas boiler installed | £2,500 – £4,500 |
The grant is available in England and Wales through 2028. Your MCS-certified installer applies for it – you don’t need to do anything yourself.
6. Choose Your Installer Carefully
The quality of installation matters far more than the brand of heat pump. A well-installed budget heat pump will outperform a premium model that’s been badly set up. Here’s what to look for:
- MCS certification – mandatory for BUS grant eligibility
- Manufacturer training – ask if they’re accredited by the specific brand
- Portfolio of similar installs – ask for references from properties like yours
- Detailed survey before quoting – including room-by-room heat loss
- Post-install commissioning – they should optimise settings over the first winter
- At least 3 quotes – prices vary by 30–50% for the same work
7. It’s Not Just About Today’s Numbers
Heat pumps are a 20–25 year investment. Over that period, gas prices will almost certainly rise (they’ve tripled in 5 years), electricity will get greener and likely cheaper relative to gas, the 2035 gas boiler ban will limit resale options for gas-heated homes, and heat pump technology will continue improving. Even if the maths are tight today, the long-term trajectory strongly favours electrification.
✅ You’re Ready If:
- Your home has EPC rating C or better
- You’ve had a professional heat loss survey
- You have outdoor space for the unit
- You’ve got 3 MCS-certified quotes
- You understand the BUS grant process
⚠️ Wait If:
- Your insulation needs work first
- Your boiler is under 5 years old
- You haven’t had a heat loss survey
- You’re moving within 3–5 years
Frequently Asked Questions
Do I need planning permission for a heat pump?
Usually no. Air source heat pumps are permitted development in England, Scotland, and Wales, provided the unit is at least 1 metre from the property boundary, doesn’t exceed 0.6m³ in volume, and isn’t on a listed building or in a conservation area (check with your local planning office if in doubt).
How long does installation take?
A straightforward retrofit takes 2–4 days. More complex installations (new radiators, underfloor heating, cylinder installation) can take 4–7 days. Your installer should provide a clear timeline before work begins.
Can I install a heat pump myself?
No. Heat pump installation must be done by an MCS-certified installer to qualify for the BUS grant, meet building regulations, and validate the manufacturer’s warranty. DIY installation voids all of these.
Ready to Learn More?
Our complete heat pump guide covers brands, costs, and the full installation process.