Most UK new-build housing is 3-bed: 3-bed semi-detached dominates volume developer sites, 3-bed detached and townhouse types fill out the mix. Under the Future Homes Standard from 24 March 2027, every new 3-bed needs solar PV covering 40% of its ground floor area — typically a 3.4 kWp array on a semi or 4.0 kWp on a detached. This page costs out the FHS-compliant package in detail.
System sizing for a 3-bed new build
The 40% PV rule is calculated against ground floor area, not total floor area. A typical UK 3-bed semi has 85 m² total floor area split over two storeys — so 42.5 m² ground floor. 40% of that is 17 m² of panel area, which is 8 standard 425W panels totalling 3.4 kWp.
A 3-bed detached is typically 95-100 m² total, with 50 m² ground floor. 40% × 50 m² = 20 m² panel area = 10 panels = 4.0 kWp. A 3-bed terrace is typically 75-80 m² total, with 38 m² ground floor. 40% × 38 m² = 15.2 m² panel area = 7-8 panels = 3.0 kWp.
Volume developer pricing — 3-bed semi (3.4 kWp)
| Item | Cost |
|---|---|
| 8 × 425W mono panels (Q CELLS / LONGi) | £1,450 |
| 5 kW hybrid inverter (SunSynk / SolarEdge) | £780 |
| In-roof mounting tray + flashings | £460 |
| Installation labour (factory pre-fit + site) | £660 |
| DC/AC cabling, isolators, monitoring | £320 |
| MCS certification, commissioning, warranty | £410 |
| Total — in-roof at build stage (~£1,200/kWp) | £4,080 |
Indicative composition — line items are an indicative split of the ~£1,200/kWp build-stage total (Spirit Energy published basis). Volume developer pricing assumes 100+ plot bulk procurement, factory pre-fit on panelised roof cassettes and amortised SAP/HEM modelling across the plot count. Spot-market pricing for one-off installations is approximately 20-25% higher.
Self-build retail pricing — 3-bed detached (4.0 kWp)
| Item | Cost |
|---|---|
| 10 × 425W mono panels (REC Alpha or equivalent premium) | £2,100 |
| 6 kW hybrid inverter with per-panel optimisation | £1,400 |
| In-roof mounting + premium flashings | £620 |
| Installation labour (small-site retail) | £1,200 |
| Cabling, monitoring, custom integration | £480 |
| MCS, EPC, SAP/HEM, project management | £600 |
| Total — self-build (0% VAT applied) | £6,400 |
Self-build retail pricing reflects single-plot economics, premium panel selection, and bespoke integration work. The 0% VAT relief on new-build self-build offsets ~£1,300 of the gross retail cost. Adding battery storage typically costs an additional £3,500-£5,500 for 10-13 kWh capacity.
Full FHS-package cost for a 3-bed
Solar PV is the single largest line item but not the only one. The full FHS-compliant package for a 3-bed semi (volume developer) breaks down approximately:
- Solar PV (3.4 kWp in-roof, ~£1,200/kWp)£4,080
- 5 kW ASHP + hot water cylinder£2,950
- Continuous mechanical ventilation (dMEV notional; MVHR where specified)£1,800
- Fabric detailing to notional values (walls 0.18, floor 0.13, roof 0.11)£1,200
- Triple-glazing upgrade (where required for SAP 10.3 compliance)£800
- Total FHS package (incremental over 2021)£10,830
- vs FHS Impact Assessment estimate£4,350 (incremental only — excludes ASHP that replaces gas)
The £4,350 figure in the Government Impact Assessment is the *incremental* cost above 2021 spec — it nets off the gas boiler (~£900) no longer being installed, the smaller existing fabric spec, and the smaller existing notional PV requirement. The £10,130 figure above is the total cash outflow on renewables and fabric — useful for sizing the package financially but not directly comparable to the IA premium.
For a fuller cost breakdown across all house sizes see our cost guide, and for an instant quote sized to your specific plot use the FHS PV calculator.