Blog · Published 2026-05-12

Solar + heat pump: the combined electrification case for UK commercial 2026

For UK commercial property with fossil-fuel heating, the combined solar PV + heat pump retrofit is the single most powerful decarbonisation intervention available. Heat pumps electrify the heating load; solar PV offsets the higher electrical demand the heat pump creates. Together they often deliver 50-80% carbon reduction in a single capital programme — and the grant economics favour the combined approach.

Why combine solar and heat pumps

Most UK commercial property uses gas for heating and electricity for everything else. A typical office: 60% gas, 40% electricity. A typical hotel with pool: 70% gas, 30% electricity. A typical factory: 50% gas, 50% electricity.

Replacing the gas boiler with a heat pump electrifies the heating load:

- Heat pump performance (COP): Modern air-source heat pumps deliver 3.0-3.5 kWh of heat per kWh of electricity. Ground-source 4.0-5.0. - Electrical load increase: Heat pump typically increases site electrical consumption by 50-150%. For an office, gas heating switch to heat pump adds 60-90 MWh/year electrical demand to a 100 MWh/year baseline. - Carbon impact: Electricity is ~50% lower carbon per kWh than gas at current grid factors (0.21 vs 0.20 kgCO2e/kWh? actually gas is 0.18 — but heat pump COP 3+ means heat-pump-delivered heat is much lower carbon than direct gas heating) - Operating cost: Heat pump heat costs 7-10p/kWh delivered (electricity at 28p ÷ COP 3.5). Gas heat costs 6-8p/kWh delivered. Roughly break-even on operating cost currently.

Solar PV transforms the economics. Self-consumed solar at LCOE 4-7p/kWh dramatically reduces the heat pump operating cost. Combined: solar+heat pump delivers heating at effective 2-3p/kWh — half the cost of gas.

The combined grant stack

PSDS strongly prefers integrated solar + heat pump + insulation packages over any single intervention. IETF similar. Typical award patterns:

PSDS (public sector): - 100% grant for combined solar + heat pump + insulation + LED + BMS - Strong scoring for integrated packages versus standalone - Typical award £500k-£5m for medium public sector body - Solar typically 15-25% of total programme capex

IETF (industrial): - 30-50% grant for combined heat decarbonisation + solar + process electrification - Solar often 10-15% of award value - Best fits: food production, chemicals, paper, automotive

Tax relief (commercial): - 100% Full Expensing on solar AND heat pump capex (limited companies) - 25% effective tax saving on combined programme

Smart Export Guarantee: - Solar export income offsets heat pump operating cost - Combined with REGO sales above 50kWp: 0.8-2p/kWh additional

For a £400,000 combined solar + heat pump retrofit, typical post-grant-and-tax economics: 30-50% reduction from gross capex.

Worked example: 8,000 m² office building

Worked example for a typical UK commercial office:

- Annual electricity: 380,000 kWh - Annual gas: 580,000 kWh (heating + hot water) - Total energy cost: £155,000/year - Scope 1+2 emissions: 175 tCO2e/year

Stage 1: Heat pump retrofit alone. - Replace gas boiler with 400 kW ASHP cascade - Capex: £320,000 (including pipework and BMS upgrade) - Full Expensing tax saving: £80,000 - Net cost: £240,000 - Operating cost: ~£59,000/year (electricity at 28p × 580,000 kWh ÷ COP 3.5) - Operating saving vs gas: ~£15,000/year - Payback: 16 years - Scope 1+2 reduction: 32% (replacing gas with grid electricity)

Stage 2: Add 150 kWp solar PV. - Capex: £135,000 - Full Expensing tax saving: £33,750 - Net cost: £101,250 - Annual generation: 142,500 kWh; 90% self-consumed by heat pump + base load - Annual saving: £36,000 (vs £101,250 cost) - Combined programme cost: £341,250 (vs £320 + £135 = £455 standalone) - Combined operating saving: £51,000/year - Combined Scope 1+2 reduction: 58% (heat pump 32% + solar 26%) - Combined payback: 6.7 years - 25-year NPV: £820,000 (positive)

The combined intervention is dramatically better than heat pump alone — 7-year payback vs 16-year payback.

The DNO connection question

Heat pump retrofit dramatically increases site electrical demand. Coupled with solar PV (which can export to the grid), this typically requires DNO connection upgrades:

- Heat pump alone: 50-200kW additional electrical demand. May require increased import capacity from DNO. - Solar PV alone: May require export capacity from DNO. - Combined: Net export is usually lower than solar alone (heat pump uses more of the generation) — DNO often more receptive.

Real-world example: a 400kW heat pump + 200kWp solar typically results in 50-200kW peak net export. Combined system often needs less DNO export headroom than standalone solar of the same size.

New connection upgrades cost £15,000-£500,000 depending on local network capacity. Get the DNO capacity study completed before finalising system sizes.

Combined application timeline

For a typical UK commercial property planning combined solar + heat pump:

Months 1-3: Energy audit + baseline. Identify intervention shortlist.

Months 4-6: RIBA Stage 2-3 design across all interventions. Heat pump sizing (typically 70% of design heat load). Solar sizing (typically 60-70% of post-retrofit electrical load). DNO capacity study.

Months 7-9: Grant application (PSDS / IETF). Match-funding evidence. Procurement strategy.

Months 10-12: Grant award (where applicable). Final design. Contractor procurement.

Months 13-18: Construction. Heat pump installation typically 8-12 weeks. Solar installation 2-6 weeks. Commissioning and integration 2-4 weeks.

Months 19-24: Performance monitoring. First-year savings verification. Carbon impact reporting.

Total end-to-end: 18-24 months for combined projects. Standalone solar can complete in 4-8 months — but loses the integrated grant advantage.

FAQs

FAQs on this topic

Is heat pump + solar always better than solar alone?

For buildings with significant fossil-fuel heating: yes. For buildings already on electric heating: heat pump adds marginal benefit. For most UK commercial property, combined is the right answer.

Does heat pump make my electricity bill higher?

Yes initially — replacing gas demand with electric demand. But heat pump COP 3+ means the kWh of heat costs less. Combined with solar, net operating cost is materially lower.

Can I get PSDS or IETF for just heat pump?

Standalone heat pump applications are possible but score lower than integrated packages. Combine with solar + insulation + LED for best results.

How does heat pump affect EPC rating?

Heat pumps typically lift commercial EPC rating by 1-2 bands. Combined with solar, often achieves EPC B (the 2030 MEES threshold) in one programme.