Are heat pumps suitable for older UK homes?

The evidence: heat pumps work in older British homes

The largest and most authoritative study on UK heat pump performance is the Energy Systems Catapult's Electrification of Heat Demonstration Project, funded by DESNZ. This trial monitored 742 heat pump installations across all UK housing types — Victorian terraces, 1930s semis, post-war bungalows, and modern detached homes — over two full heating seasons.

The headline finding: heat pumps achieved a median Seasonal Coefficient of Performance (SCOP) of 2.94 across ALL housing types and ages. Homes built pre-1919 had a slightly lower but still robust median SCOP of 2.77. To translate: for every 1 kWh of electricity consumed, the heat pump delivered 2.77–2.94 kWh of heat. Compare that to a 92% efficient gas boiler (0.92 kWh heat per 1 kWh of gas input). The heat pump is roughly 3x more efficient.

The EST's earlier field trials (2010–2014) painted a more mixed picture, but those installations used first-generation technology and, critically, often lacked proper system design. The 2023 EoH trial data reflects current-generation hardware installed with proper heat loss calculations and emitter sizing — and the results validate that heat pumps are viable technical solutions for the vast majority of British homes.

UK housing stock: what you're working with

According to the English Housing Survey 2022–23, the age distribution of the English housing stock: Pre-1919: 20% (4.9 million homes), 1919–1944: 18%, 1945–1964: 20%, 1965–1980: 22%, 1981 onwards: 20%. That means approximately 38% of English homes were built before the era of cavity wall insulation and modern building standards.

A typical Victorian mid-terrace has solid 9-inch brick walls with a U-value of roughly 2.0 W/m²K. A modern cavity wall with 100mm insulation: ~0.3 W/m²K. The heat loss through walls alone is 6–7x greater in the uninsulated Victorian property. This doesn't mean a heat pump won't work — it means the heat pump must be sized for the higher heat loss, and the economics shift if insulation isn't addressed.

What determines whether it works or fails

The three factors that separate successful older-home heat pump installs from failures:

**1. Heat loss calculation:** A proper room-by-room heat loss survey (following MIS 3005, the MCS standard for heat pump design) is non-negotiable. Installers who size heat pumps from rule-of-thumb floor area calculations are the single biggest cause of poor performance. A correctly sized heat pump in a draughty Victorian house will work. An undersized one won't. The calculation must account for actual wall U-values, window types, air change rates, and exposure — not just floor area.

**2. Insulation — where it counts:** Loft insulation to 300mm (current Building Regs standard) costs £300–700 and is the single most cost-effective measure. Cavity wall insulation for homes built 1920s–1980s: £500–1,500, often with grant support via ECO4. Solid wall insulation (internal or external): £5,000–12,000++ — a major investment that may change the building's character. For listed buildings and conservation areas, internal insulation is complex and requires careful detailing to avoid interstitial condensation.

The strategy that works: insulate what's practical and cost-effective first (loft, cavity if possible, draught-proofing), then size the heat pump to match the resulting heat loss. You do not need Passivhaus levels of insulation for a heat pump to work.

**3. Emitter sizing:** Heat pumps operate at lower flow temperatures (35–55°C) than gas boilers (60–75°C). Underfloor heating is ideal (runs at 35–40°C) but retrofitting it costs £6,000–12,000 per floor. Radiators must be upsized: a radiator that delivered 1.5kW at 70°C flow delivers only ~0.7kW at 45°C. The solution isn't complicated — fit larger radiators or double-panel convectors (K2, P+ types from Stelrad, Myson, or Quinn). Cost per radiator upgrade: £150–400 fitted, total £1,000–3,000 for a typical home.

Real running costs: heat pump vs gas boiler at 2026 prices

Gas price (Ofgem cap, Jan 2026): approximately 6.3p/kWh. With a 92% efficient boiler, effective heat cost: 6.8p/kWh.

Electricity (Ofgem cap): approximately 24.9p/kWh. With a heat pump at SCOP 3.0: effective heat cost: 8.3p/kWh.

At those numbers, a heat pump costs roughly 22% more per unit of heat than gas. However, this calculation ignores standing charges, boiler service costs (£80–120/year), and the value of the Boiler Upgrade Scheme (£7,500 grant). If you have solar panels supplying daytime electricity, or you're on a time-of-use tariff charging a battery overnight at 7–8.5p/kWh, the running cost equation flips in the heat pump's favour.

For off-gas-grid homes (oil or LPG heating), the comparison is dramatically different. Heating oil at ~8.5p/kWh with an 85% efficient boiler gives effective heat at 10p/kWh. An LPG boiler at ~11p/kWh effective. The heat pump at 8.3p/kWh is cheaper from day one — saving £200–400/year immediately.

Noise and planning: the practical considerations

Air source heat pumps produce 40–60 dB at 1 metre — comparable to a refrigerator (40dB) to a normal conversation (60dB). MCS planning standards (MCS 020) require the sound level at the nearest neighbour's habitable window not to exceed 42 dB. For most detached and semi-detached homes with sensible siting, this is easily met. For terraced homes with limited external space, siting becomes critical. Some modern units (Vaillant aroTHERM plus, Daikin Altherma 3, Mitsubishi Ecodan) operate at remarkably low noise levels of 48–54 dB at full load.

Planning permission: heat pumps are permitted development (no planning required) under Class G of the General Permitted Development Order, provided they meet conditions on size (max 0.6m³), noise, and siting. Listed buildings and conservation areas may require additional consent — always check with the local planning authority.

Cost summary: what you'll actually spend

Air source heat pump installation (5–7kW, typical 3-bed semi): £8,000–12,000 before BUS grant. After £7,500 BUS grant: £500–4,500 net. Add radiator upgrades: £1,000–3,000. Add hot water cylinder if not already present: £800–1,500. So a realistic total after grant: £2,000–7,500.

The 0% VAT rate on energy-saving materials saves an additional £1,200–1,800 on the pre-grant figure. For off-gas-grid homes, the payback on this investment (vs continuing with oil/LPG) typically falls within 4–7 years. For on-grid gas homes, the financial case depends more on environmental priorities, solar/battery integration, and future gas-vs-electricity price projections.