What is the cost per kWp for commercial solar in the UK?

Cost per kWp (kilowatt-peak) for UK commercial solar in 2026 sits at £900-£1,200 below 100 kWp, £750-£950 between 100-500 kWp, and £700-£850 above 500 kWp. kWp refers to the rated DC capacity of the panel array under Standard Test Conditions (1,000 W/m², 25°C, AM1.5). It’s the figure quoted on the panel datasheet and the basis for almost all UK installer pricing. Don’t confuse it with kWac, which is the inverter output capacity, or with annual kWh generation, which is what actually reaches your meter.

kWp, kWac, and kWh — what each one means

This terminology trips up almost every SME buyer:

• kWp (kilowatt-peak): DC nameplate capacity of the panels. A “100 kWp system” has 100 kWp of panels.
• kWac: AC output capacity of the inverters. Often slightly smaller than kWp because installers oversize panels relative to inverter (typical DC:AC ratio of 1.1-1.3).
• kWh: actual energy generated over time. A 100 kWp UK system produces 85,000-105,000 kWh/year.

When you compare quotes, always confirm the £/kWp figure refers to DC panel capacity. If one quote says “£800/kWp” and another says “£1,000/kWp” but the second is actually £1,000/kWac on a 1.2 DC:AC ratio system, the second quote is cheaper per kWp (~£833/kWp).

What’s included in £/kWp

A turnkey £/kWp figure should include all of the below — confirm in writing before signing:

1. Panels and mounting hardware
2. Inverters and DC isolators
3. AC cabling to consumer unit
4. Smart export meter
5. Scaffolding, access, edge protection
6. Structural roof survey
7. DNO connection application (G98 or G99)
8. MCS commissioning and certification
9. Building control sign-off
10. 10-year insurance-backed workmanship warranty
11. 25-year panel output warranty (manufacturer-backed)
12. 10-12 year inverter warranty (manufacturer-backed)

What’s typically NOT in £/kWp

• VAT (20% standard rate on commercial)
• Battery storage (£450-£700/kWh)
• Three-phase upgrade (£2,500-£8,000)
• Asbestos management plan (£5,000-£20,000)
• Roof structural reinforcement (£8,000-£40,000)
• DNO connection charge for large G99 (variable, can be £15k-£250k+)
• Ongoing monitoring service contract (£200-£500/year)

Worked example: 80 kWp office install

A daytime-occupied office, 80 kWp system, £900/kWp = £72,000 headline. Annual generation 72,000 kWh. At 65% self-consumption and 38p/kWh grid avoidance plus 35% export at 8p/kWh blended SEG: annual saving £19,800. After AIA: net cost £54,000. Payback: 2.7 years.

The same 80 kWp system on a weekend-only retail site without batteries: self-consumption drops to 35%, annual saving falls to about £11,500, payback stretches to 6.3 years before tax relief.

Common misconceptions about £/kWp

The biggest: that low £/kWp = best value. A £700/kWp quote with Tier 2 panels and a basic string inverter may underperform a £950/kWp quote with Tier 1 panels, optimisers, and panel-level monitoring by 8-12% over 25 years. On a 100 kWp system that’s £30,000-£40,000 of lost savings.

The second: that £/kWp shrinks every year. Module prices fall, but UK labour, scaffolding, copper cabling, and DNO fees rise. Total £/kWp has been roughly flat since 2023.

Next steps

For a fixed £/kWp quote including 25-year generation modelling, contact us. See the broader cost breakdown and grants page. Related: cost per kW, panel efficiency, total cost.