Solar Panels on London Properties: Planning, Costs & What to Expect
Solar photovoltaic (PV) panels are a common addition to London homes — particularly during roof replacements, extension projects, and energy efficiency upgrade programmes. Installation is usually permitted development, costs have fallen significantly, and energy payback periods are increasingly viable.
Planning Permission for Solar Panels
Solar PV panels on residential properties are generally permitted development — planning permission is not required for:
- Panels on a pitched roof that do not protrude more than 200mm from the roof plane
- Panels on a flat roof or extension roof that do not protrude more than 200mm above the highest point of the roof
Restrictions:
- Listed buildings require Listed Building Consent for any external alteration including solar panels
- In World Heritage Sites and some specific conservation area designations, panels visible from the highway are not permitted development — check with your LPA before installation
In most London conservation areas, panels on rear roof slopes that are not visible from the street are permitted development.
Realistic Solar Output in London
London's latitude means solar output is lower than southern Europe but still commercially viable. A typical south-facing 4kWp system in London generates approximately 3,400–3,800 kWh per year. East-west-facing configurations generate approximately 80–90% of south-facing output but spread generation across more of the day.
System Sizing
For a typical London 3–4 bedroom family home:
- 10–14 panels (375–400W each) provides a 4–5kWp system
- Annual generation of approximately 3,500–4,500 kWh
- Self-consumption of 30–50% typically, depending on household patterns
- Battery storage increases self-consumption to 60–80%
Typical Costs
| System size | Approximate installed cost (supply and fit) |
|---|---|
| 3kWp (8 panels, no battery) | £5,000–£7,500 |
| 4kWp (10 panels, no battery) | £6,000–£9,000 |
| 4kWp + 5kWh battery storage | £9,000–£14,000 |
| 6kWp + 10kWh battery storage | £13,000–£20,000 |
Energy costs used for payback calculation should reflect current and projected tariff rates. At current UK energy prices, payback periods of 8–12 years are typical for the system alone, reducing to 6–9 years with battery storage and smart EV charging.
Smart Export Guarantee (SEG)
Electricity exported to the grid earns the SEG tariff — licensed suppliers with 150,000+ customers must offer a SEG tariff. Rates vary between suppliers. The grid export income adds to the financial case.
Integration with Extensions and Loft Conversions
A roof replacement or new extension flat roof is the ideal time to install solar — the cost of electrical work (inverter, consumer unit connection) is shared with the other M&E works, and no extra scaffolding is required.
RCB Design & Build
RCB Design & Build includes solar PV installation as part of extension and renovation projects — coordinating the installation with the roofing and electrical programme.