Last updated: March 13, 2026 | By Evolving Home
The Real Cost and ROI of Heat Pumps vs Insulation in UK Homes (2026)
The question everyone's asking wrong
"Should I get a heat pump or insulate?" is the most common energy upgrade question in the UK right now. And it's the wrong question — because the answer is almost always insulate first, then consider a heat pump.
But nobody wants to hear that, because heat pumps are exciting and loft insulation is boring. So let's look at the actual numbers for real UK house types, using real 2026 costs, real grant amounts, and honest payback periods.
Spoiler: for most UK homes, £1,000 of insulation saves more energy than £10,000 of heat pump. The order you do things in matters enormously.
The current cost landscape (March 2026)
Energy prices
- Gas: 5.74p/kWh (Ofgem cap Q1 2026), dropping to ~5.5p from April
- Electricity: 24.5p/kWh (Q2 2026 cap)
- Electricity-to-gas ratio: ~4.3:1
This ratio is critical. A heat pump needs to deliver roughly 3.5–4x as much heat per kWh of electricity as a gas boiler does per kWh of gas just to break even on running costs. That's achievable for a well-installed system in a well-insulated home — but it's tight.
Heat pump costs (before grants)
| System type | Cost range |
|---|---|
| Air-source (ASHP) | £7,000–£13,000 |
| Ground-source (GSHP) | £15,000–£25,000 |
| Hybrid heat pump | £5,000–£9,000 |
The Boiler Upgrade Scheme (BUS) grant
The government offers £7,500 off an ASHP or GSHP through the BUS. This is the single biggest factor in heat pump economics right now. With the grant, a typical ASHP costs £2,500–£5,500 out of pocket. VAT is currently 0%.
Important: The BUS is funded through March 2028. Take-up is accelerating. If you're considering a heat pump, the £7,500 grant makes it a fundamentally different financial proposition — and it won't be available indefinitely.
Insulation costs
| Measure | Cost | Annual saving | Payback |
|---|---|---|---|
| Loft insulation (0→300mm) | £300–£600 | £150–£300 | 2 years |
| Cavity wall insulation | £500–£1,500 | £150–£350 | 3 years |
| Draught-proofing | £200–£500 | £50–£150 | 3.5 years |
| Solid wall (external) | £8,000–£15,000 | £200–£500 | 20+ years |
| Solid wall (internal) | £4,000–£9,000 | £150–£400 | 15–20 years |
House-by-house breakdown: what actually makes sense
1. Pre-1930 solid-wall terrace (EPC D/E)
Victorian or Edwardian terrace, 2–3 bed, gas boiler, old glazing, no cavity walls.
This is the hardest house type in Britain to decarbonise. Solid walls are expensive to insulate, and the building fabric is so leaky that a heat pump has to work overtime — killing its efficiency.
At COP 2.5, your electricity cost per kWh of heat is 24.5p ÷ 2.5 = 9.8p/kWh — compared to gas at about 6.4p/kWh. You'd pay more to heat with a heat pump.
Verdict: Insulate everything you can afford first. The heat pump only makes sense once you've reduced heat demand enough for COP 3.0+.
2. 1950s–1970s cavity-wall semi (EPC D) — The sweet spot
Post-war semi, 3 bed, unfilled cavity walls, gas combi boiler.
Cavity wall insulation is cheap and effective. Once walls and loft are sorted, the heat pump achieves COP 3.0–3.5. At COP 3.2, electricity cost per kWh of heat is 7.7p/kWh — close to gas.
Optimal sequence:
- Cavity wall + loft top-up: £1,150 → payback 3 years
- ASHP with BUS grant: £3,500 → payback 10–14 years
- Total spend: £4,650 → annual saving: £550–£700
Verdict: Insulate first (it's so cheap it's almost criminal not to), then get the heat pump with the BUS grant while it's available.
3. 1990s–2000s detached (EPC C)
Modern estate house, 4 bed, filled cavities, decent loft, gas boiler.
Already reasonably efficient. The heat pump achieves COP 3.5–4.0. At COP 3.5, electricity cost is 7.0p/kWh — genuinely competitive with gas.
Hidden win: Add solar panels and battery. The heat pump runs partly on free electricity during sunny hours. Marginal heating cost drops toward zero.
Verdict: Top up loft (£250), then ASHP with grant. If planning solar anyway, do both — the synergies are significant.
4. Post-2010 new build (EPC B)
The economic case for a heat pump is strongest here but the savings are modest because baseline bills are already low. Payback: 14–23 years.
Verdict: Do it for the planet, not the payback. The BUS grant makes it affordable, and you future-proof against potential gas boiler restrictions from 2035.
The numbers the industry doesn't show you
1. Real-world COP is 2.8–3.2, not 4.0+. Manufacturers quote lab conditions. UK field data from the Electrification of Heat project shows lower real-world performance.
2. You might need bigger radiators. Heat pumps work best at low flow temperatures. Budget £1,500–£4,000 for radiator upgrades. This cost is often missing from quotes.
3. Insulation has no moving parts. Loft insulation from 2026 will still work in 2066. A heat pump needs replacing in 15–20 years.
4. The electricity-to-gas price ratio is everything. If the government rebalances energy levies (moving green levies from electricity to gas), heat pump economics improve dramatically overnight.
What should you actually do?
Step 1: Insulate. Always. Loft and cavity walls are the highest-ROI home improvements available. 2–4 year payback.
Step 2: Assess properly. Your heating decision depends on fabric, heat loss, and radiator sizes — not just your EPC letter.
Step 3: Sequence correctly. Insulate → assess heat demand → size the heat pump → install. Wrong order = oversized, inefficient system.
We built our scoring system to do exactly this: model your fabric performance, calculate real heat demand, and give you a sequenced upgrade plan with honest costs.
Sources: Ofgem price cap data (Q1/Q2 2026), BEIS Electrification of Heat Demonstration Project, BUS grant terms (Ofgem, March 2026), EST insulation cost estimates, MCS installer data, Energy Saving Trust heating cost comparisons.