4-bed homes are the second-largest segment of UK new-build delivery after 3-beds — and the segment where homeowner solar economics are most attractive. The larger floor area requires a bigger PV array (5.2 kWp typical vs 3.4 kWp on a 3-bed), but the larger household energy use absorbs more of the generation, lifting self-consumption rates and pulling forward payback. This page costs the FHS-compliant package for both detached and semi-detached 4-bed types in 2026.
Sizing for a 4-bed: detached vs semi-detached vs townhouse
FHS sizing is a function of ground floor area, which varies materially across 4-bed house types. A 4-bed detached typically has 50-65 m² ground floor; a 4-bed semi 45-55 m²; a 4-bed townhouse 35-40 m² (smaller because spread across 3 storeys). At the 40% PV rule:
| 4-bed house type | Ground floor | Panel area | kWp |
|---|---|---|---|
| 4-bed detached (entry) | 50 m² | 20 m² | 4.0 kWp |
| 4-bed detached (standard) | 65 m² | 26 m² | 5.2 kWp |
| 4-bed detached (large) | 80 m² | 32 m² | 6.4 kWp |
| 4-bed semi (typical) | 50 m² | 20 m² | 4.0 kWp |
| 4-bed townhouse | 38 m² | 15 m² | 3.0 kWp |
Volume developer pricing — 4-bed detached (5.2 kWp)
| Item | Cost |
|---|---|
| 12 × 425W mono panels (Q CELLS / LONGi) | £1,820 |
| 6 kW hybrid inverter | £860 |
| In-roof mounting (larger area) | £620 |
| Installation labour | £560 |
| Cabling, monitoring | £310 |
| MCS, commissioning, warranty | £330 |
| Total PV — developer volume | £4,500 |
Self-build retail — 4-bed detached (5.2 kWp + 13 kWh battery)
| Item | Cost |
|---|---|
| 12 × 425W premium panels (REC Alpha Pure) | £2,520 |
| 8 kW hybrid inverter with optimisers | £1,650 |
| In-roof premium mounting + flashing | £780 |
| Installation labour | £1,400 |
| Cabling, monitoring, custom integration | £520 |
| SAP/HEM, MCS, project management | £680 |
| Subtotal — PV only | £7,550 |
| 13 kWh battery (GivEnergy All-In-One) | £5,800 |
| Total — self-build (0% VAT applied) | £13,350 |
Annual savings for a 4-bed
A 5.2 kWp south-facing array in the South Midlands generates approximately 4,900 kWh/year. A typical 4-bed household with ASHP heating, electric cooking and 1 EV uses ~9,000 kWh/year. Self-consumption without battery: ~55% (panels generating during the day when occupants are out). With a 13 kWh battery: ~78%.
| Scenario | Self-consumed | Exported | Annual £ benefit |
|---|---|---|---|
| 5.2 kWp PV alone | 2,695 kWh | 2,205 kWh | £770 |
| 5.2 kWp + 13 kWh battery | 3,820 kWh | 1,080 kWh | £1,050 |
Self-consumed kWh valued at 22p (grid retail tariff). Exported kWh at 8p (SEG average). PV-only payback on a £4,500 volume developer install: 5.8 years. Self-build with battery (£13,350): 12.7 years simple payback.
See also: 3-bed pricing, 5-bed pricing, and the full FHS cost overview.