Payback
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.
Commercial solar payback in the UK lands at 5-8 years for most SMEs in 2026. After 100% Annual Investment Allowance tax relief, the figure drops to 3-5 years for a profitable limited company at 25% corporation tax. The actual figure for your site depends on three things: how much of the generation you can self-consume, what you’re paying for grid electricity now, and whether you finance, buy, or PPA the system. Daytime-occupied sites with high baseload — manufacturing, retail, garden centres — sit at the low end. Office-only sites with weekend dark periods run 7-9 years. Adding battery storage extends payback by 2-3 years but increases lifetime savings by 25-40%.
What “payback” actually means
Simple payback period = total install cost divided by annual saving. It’s the count of years until the system has paid for itself in saved electricity bills. After payback, every saving year is profit.
Two payback figures matter:
- Pre-tax payback — capex / annual saving. This is the figure cowboys love because it ignores tax.
- Post-AIA payback — (capex × 0.75) / annual saving. The figure for a profitable Ltd. Subtract roughly 25% from the headline cost because AIA tax relief refunds it.
Worked payback examples
75 kW office install
- Capex: £71,000
- Annual saving (year 1): £15,500
- Pre-tax payback: 4.6 years
- Post-AIA payback: 3.4 years
180 kW light-industrial install
- Capex: £162,000
- Annual saving (year 1): £42,000
- Pre-tax payback: 3.9 years
- Post-AIA payback: 2.9 years
50 kW retail showroom (weekend-quiet)
- Capex: £52,000
- Annual saving (year 1): £8,500
- Pre-tax payback: 6.1 years
- Post-AIA payback: 4.6 years
Why payback varies so widely between sites
The single biggest driver is self-consumption rate. A 100 kW system on a 24/7 manufacturing site might self-consume 90% of generation at full grid avoidance value (~38p/kWh). The same system on a Monday-Friday office self-consumes 55% and exports the rest at SEG rates (4-15p/kWh).
The maths:
- 90% self-consumption + 10% export at 5p: blended saved value ~35p/kWh
- 55% self-consumption + 45% export at 5p: blended saved value ~23p/kWh
That’s a 50% difference in annual saving for the same kit, driving payback from ~3 years to ~6 years.
How financing affects payback
| Funding route | Effect on payback |
|---|---|
| Cash purchase + AIA | 3-5 year payback. Best long-run economics. |
| Asset finance (7-year) | Cash-flow positive month 1; full payback at end of year 7 (when finance ends). |
| PPA (zero capex) | “Payback” doesn’t apply — savings start day 1, no capex outlay. Discounted electricity rate over 15-20 year term. |
| Operating lease | Similar to asset finance but VAT-recoverable monthly rather than upfront. |
Common misconceptions about payback
“Payback only matters if I plan to stay 8 years” — wrong. Solar improves your building’s commercial value (5-15% uplift documented) and the asset transfers with the property. If you’re a tenant, the system can be relocated (15-25% of original cost) or sold to your landlord at residual value.
“Payback is shorter than it used to be” — true. In 2021, with grid at 14p/kWh, commercial payback was 9-12 years. At today’s 35-50p commercial tariffs, it’s 5-8 years. If grid prices fall back to 2021 levels, payback would extend — but the FIT-era subsidy regime is what drove the old figures, not low electricity.
“Faster payback = better project” — not always. A 3-year payback on a 30 kW system saves £4,000/year. A 5-year payback on a 200 kW system saves £40,000/year. Total IRR usually beats the smaller faster project.
Next steps
For a payback model from your meter data, request a free feasibility study. See our cost guide and grants and funding page. Related: payback period detail, annual savings, system sizing.
Related questions
How much does a 100 kW commercial solar system cost?
A 100 kW commercial solar system in the UK costs £85,000-£110,000 turnkey in 2026, depending on roof type, three-phase status, and whether optimisers are specified. Typical annual generation is 90,000-95,000 kWh, saving £20,000-£25,000/year for a daytime-occupied SME at current grid prices. Simple payback lands at 4-5 years before tax relief, 3-4 years after AIA.
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 (4-15p/kWh) for the rest. Lifetime savings over 25 years usually total £350,000-£550,000 on a £85,000-£100,000 install.
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.