7kW Solar System UK: Cost, Output and Who It's For

A 7 kilowatt-peak (kWp) solar system fills the gap between the two most common residential sizes in the UK — 6 kW and 8 kW. It suits large family homes that consume more than the 6 kW size comfortably covers but don't quite need the roof space or budget an 8 kW array demands. Here is what a 7 kW system consists of, what it costs, how much it generates, and whether it's the right fit for your home in 2026.

What Does a 7 kW Solar System Consist Of?

Panels, inverter, and mounting. A 7 kWp array uses 17 to 19 monocrystalline panels depending on wattage. At 375 W per panel you need 19 panels; at 400 W, 18 panels; at 420 W, 17 panels. You need roughly 33–38 m² of unshaded roof area — typically a large single pitch on a detached or big semi-detached house, or a main south-facing slope topped up with a handful of panels on a secondary pitch. For a breakdown of panel dimensions and how many will physically fit, see our solar panel dimensions and roof layout guide.

Inverter and battery pairing. Most 7 kW installs use a single string inverter rated for the full AC output, or a hybrid inverter if a battery is part of the plan from the outset. A 10–13 kWh battery is the natural companion size — large enough to absorb the midday surplus a 7 kW array produces on a sunny day without excess spill to export. See our home battery storage guide for capacity and chemistry options.

How Much Does a 7 kW Solar System Cost in the UK?

Typical installed cost: £8,500–£12,500. This sits between the £7,500–£11,000 range for a 6 kW system and the £9,500–£14,000 range for an 8 kW system. A straightforward install on an accessible pitched roof in the South East or Midlands, using a mid-range inverter, typically falls in the £9,000–£10,500 bracket. Roof complexity, scaffolding access, and premium inverter brands (SolarEdge, Fronius, SMA) push costs toward the upper end.

VAT is zero-rated. Under legislation in force until 31 March 2027, installing solar PV panels in residential homes in Great Britain carries 0% VAT. This covers panels, inverter, mounting hardware, cabling, and a battery when fitted alongside qualifying solar equipment. After that date, the rate reverts to 5%.

Battery add-on. A 10–13 kWh AC-coupled battery adds roughly £4,000–£5,500 to the total, also at 0% VAT when installed with qualifying solar. A combined 7 kW solar plus 12 kWh battery system typically costs £12,500–£18,000 installed.

Annual Output: How Much Electricity Will You Generate?

Approximately 5,700–6,300 kWh per year for a south-facing roof at 30–40° tilt in central England, based on PVGIS modelling by the European Commission Joint Research Centre. Output falls to around 5,300 kWh in Scotland and rises to around 6,500 kWh in Devon or Kent. These figures assume around 14% system losses from inverter conversion, cabling, and temperature effects.

For context, a 6 kW system in the same conditions generates around 5,000–5,400 kWh, and an 8 kW system around 6,400–7,200 kWh — so 7 kW sits roughly in the middle, adding around 15% more generation than 6 kW for a proportionally smaller cost increase than jumping straight to 8 kW. See our solar panel output by month in the UK for the seasonal generation curve to plan around.

East–west split. If your best roof space is split between east and west pitches rather than a single south-facing slope, a divided array (roughly 9 panels each side) achieves around 80–85% of the south-facing yield but spreads generation across more of the day — useful for households charging an EV both morning and evening.

Who Is a 7 kW System Best Suited To?

Large households just above the 6 kW threshold. If your consumption sits around 5,500–6,000 kWh a year — more than a 6 kW system comfortably self-consumes, but not enough to justify an 8 kW roof commitment — 7 kW is often the better-value middle ground. This typically means a 4–5 bedroom home with above-average daytime occupancy.

EV owners with moderate mileage. Home EV charging adds roughly 2,000–4,000 kWh a year depending on annual mileage. A 7 kW solar system can cover a large share of that from daylight generation, with a battery handling the rest via overnight or off-peak charging. Our guide to solar EV charging and smart scheduling covers how to line up charging windows with generation.

Heat pump households. An air source heat pump typically adds 2,000–4,000 kWh of electrical demand a year. Combined with a battery, a 7 kW array can meaningfully offset that load from spring through autumn, when heating demand and solar generation overlap most.

Homes with limited roof space for 8 kW. Not every large house has the 36+ m² of clear, unshaded roof an 8 kW array needs. If your usable roof area sits closer to 33–36 m² once dormers, chimneys, or Velux windows are accounted for, 7 kW is often the practical ceiling rather than a compromise.

G99: The DNO Notification Requirement Above 3.68 kW

A 7 kW system exceeds the G98 single-phase limit of 3.68 kW, so it falls under the G99 process. Your installer must submit a G99 application to your local Distribution Network Operator (DNO) before the system is commissioned. Under the G99 fast-track process, DNOs must respond within 10 working days for systems below 14.72 kW, and residential rooftop approvals in this size range are routine.

You remain the responsible party as the system owner even though your MCS-certified installer submits the paperwork on your behalf — ask them to confirm the application has been made and approved before switch-on. GOV.UK publishes guidance on registering energy devices covering both G98 and G99 processes. If your property already has a three-phase supply, a 7 kW system sits comfortably below the 11.04 kW three-phase G99 threshold, which can simplify approval.

Smart Export Guarantee: What You Earn on Surplus

Export tariffs are set by individual suppliers, not the government, and must legally be greater than zero. Typical fixed-rate SEG tariffs in 2026 run from around 3p to 15p per kWh, with the best widely available fixed rates (Octopus Outgoing, OVO, E.ON Next) reaching 12–15p/kWh. Ofgem publishes the full Smart Export Guarantee framework.

A 7 kW system on a household consuming 5,500–6,000 kWh a year might self-consume around 2,800–3,300 kWh and export 2,400–2,900 kWh. At 13p/kWh export, that's roughly £310–£380 a year in SEG payments on top of import savings.

Bill Savings and Payback

Annual bill saving: £900–£1,500. Based on the Ofgem Q2 2026 price cap unit rate of 24.67p/kWh, self-consuming 2,800–3,300 kWh saves roughly £690–£810 a year on imports. Add SEG export income and diverter-boosted hot water, and a realistic combined benefit is £1,000–£1,200 a year without a battery, rising toward £1,500 with a battery that cuts evening peak imports.

Payback period: 8–11 years. At a net install cost of £10,000 and annual savings of £1,050, payback lands around 9.5 years — comfortably inside the typical 25-year panel warranty. Households with an EV or heat pump that increase self-consumption usually see faster payback than the average.

How to Get the Right Quote

Use an MCS-certified installer — MCS certification is the minimum requirement for Smart Export Guarantee eligibility and any grant funding. Get at least three quotes; price variation of 20–30% between installers for the same specification is common. Ask each installer for their G99 submission plan, the panel brand and warranty terms, and the inverter model, and be wary of quotes that omit scaffolding, DC isolators, or generation metering.