Payback
What is the payback period for commercial solar panels?
Commercial solar panels typically pay back in 5-8 years in the UK in 2026, with the median around 6.5 years. Profitable limited companies using 100% AIA tax relief see payback fall to 3-5 years. The asset then continues generating savings for another 17-22 years before requiring inverter replacement, with panels still producing 87% of original output at year 25.
Commercial solar panels typically pay back in 5-8 years in the UK in 2026, with most SME projects landing at around 6.5 years on a simple pre-tax basis. For profitable limited companies, 100% Annual Investment Allowance brings post-tax payback down to 3-5 years. After payback, the panels keep generating for another 17-22 years before the inverter typically needs replacement around year 11, with Tier 1 panels still producing 87-90% of original nameplate at year 25. The total return profile is unusually attractive in industrial finance terms: short payback, long tail.
The payback maths in plain numbers
Take a 120 kW install on a daytime-occupied office at £108,000 turnkey.
- Annual generation: 110,000 kWh
- Self-consumption: 65% at 38p/kWh = £27,170 grid avoided
- Export: 35% at 5p/kWh blended SEG = £1,925
- Year-1 saving: £29,095
- Pre-tax payback: 3.7 years
- Post-AIA payback: 2.8 years (capex effective £81,000 after tax relief)
Compare with the same 120 kW system on a retail outlet that closes at 6pm and is shut Sundays:
- Annual generation: 110,000 kWh
- Self-consumption: 45% at 38p/kWh = £18,810 grid avoided
- Export: 55% at 5p/kWh blended SEG = £3,025
- Year-1 saving: £21,835
- Pre-tax payback: 4.9 years
- Post-AIA payback: 3.7 years
Why payback shouldn’t be your only metric
Payback period is intuitive but it’s a poor stand-alone investment metric. It ignores everything that happens after the payback point. A better approach is internal rate of return (IRR) or net present value (NPV) over a 25-year asset life.
Typical UK SME commercial solar IRRs in 2026:
- Cash purchase, daytime occupancy, AIA-eligible: 18-28% IRR
- Cash purchase, mixed occupancy, AIA-eligible: 12-20% IRR
- Asset finance, any occupancy: 25-40% IRR (because you only deploy a small portion of capital upfront)
- PPA: 0% IRR (zero capex), but day-one cash savings of 10-25% off grid rate
Even at the low end, those returns dwarf typical SME alternative investments — fixed-rate cash deposits at 4-5%, corporate bonds at 6-8%.
The 25-year shape of returns
| Year | Status | Cumulative cashflow (illustrative 100 kW @ £92k) |
|---|---|---|
| 0 | Install paid | -£92,000 |
| 1 | First full year saving £22k, AIA refund £23k | -£47,000 |
| 5 | £110k cumulative saving | +£18,000 |
| 11 | Inverter replacement -£12k | +£148,000 |
| 25 | End of warranty, panels still 87% output | +£480,000 |
That’s the full 25-year story. Most SMEs we work with focus on the first 7 years (until asset finance is paid off). The next 18 years are pure profit.
Common misconceptions about payback
“Solar payback was 9 years pre-2022 and now it’s 5 years — must be subsidies” — no. The 2010-2019 figures were driven by Feed-in Tariff (FIT) subsidies; FIT closed in 2019. The 2026 payback improvement is driven entirely by grid electricity prices rising 100-200% since 2021. Solar economics improved because grid economics worsened.
“Payback resets if I sell the building” — no. The asset transfers with the property at residual value. RICS valuation guidance recognises commercial PV as a value-adding fixture (5-15% premium typical).
“After payback there are no more costs” — slight oversimplification. Inverters need replacement around year 11 (£8,000-£15,000 for a 100 kW system). Panels rarely fail. Cleaning is optional. Annual monitoring contract is £200-£500.
Next steps
For a fixed-price payback model from your meter data, request a free feasibility study. See our cost page, grants and funding overview, and asset finance options. Related: payback overview, panel lifespan.
Related questions
What's the payback period for commercial solar in the UK?
Commercial solar payback in the UK is 5-8 years for most SMEs in 2026, dropping to 3-5 years after 100% AIA tax relief for profitable limited companies. Payback depends on self-consumption, grid tariff, and system size. Daytime-occupied sites with high baseload (manufacturing, retail) hit the lower end; office-only sites with weekend gaps run 7-9 years.
How much can a business save with solar panels?
A typical UK SME with a 100 kW solar system saves £18,000-£25,000 per year at current commercial electricity prices. Savings come from displaced grid imports (largest share, around 60-75% of generation) and SEG export payments (4–12p/kWh) for the rest. Lifetime savings over 25 years usually total £350,000-£550,000 on a £85,000-£100,000 install.
How long do commercial solar panels last?
Commercial solar panels last 30-40 years physically with Tier 1 manufacturers offering 25-year linear performance warranties at 87% of nameplate. Inverters typically need replacement once around year 11. Real-world UK installs from 1995-2000 are still operating at 80-85% of original output. Asset life is typically constrained by inverter and switchgear, not the panels themselves.
Common concerns, answered honestly
"What if we move premises?"
A common objection — and a fair one. If your remaining lease is under five years, a PPA (the funder owns the system, you buy the power) usually beats an outright purchase, or we build roof-rights portability into the deal. We model lease length explicitly and tell you if solar genuinely isn't the right fit.
"What if the roof needs work?"
We survey the roof structure before quoting. Older or asbestos-cement roofs are costed transparently up front — no surprises after contract. See roof suitability for the full checklist.
"What if payback takes too long?"
Typical UK commercial payback is 5–8 years against a 25-year asset — but we won't oversell it. If your load profile or tariff doesn't stack up, our savings calculator and free desk feasibility will show you honestly. See is it worth it?