Commercial solar ROI: what payback period can a UK business expect in 2026?
The short answer: most UK businesses see a payback period of 3.5–5.5 years on commercial solar, with a pre-tax return (IRR) of 18–28% over the system's 25-year life. This guide covers the metrics finance teams actually use - simple payback, discounted payback, IRR, NPV and lifetime unit cost - with worked examples for 100 kWp to 1 MWp systems, ROI by industry, and the six levers that move returns most.
By Mike Davies, Managing Director, Solar Britain · Published 20 July 2026.
Key takeaways
- UK commercial solar systems typically achieve payback within 3 to 6 years, delivering annual returns on investment between 15% and 25%.
- Returns are driven by onsite self-consumption, HMRC Full Expensing tax relief, and selling surplus generation back to grid suppliers via Smart Export Guarantee.
- Accurately matching panel capacity to weekday electricity demand maximises financial returns and protects businesses against volatile commercial grid energy tariffs.
Short answer
Typical UK commercial solar in 2026: simple payback 3.5–5.5 years, pre-tax IRR 18–28%, 25-year NPV at 8% discount of 1.5x–3x net CapEx, and lifetime unit cost around 3.5–5p/kWh versus a grid average of 26p/kWh. Full Expensing on limited-company CapEx returns 25p per £1 in year one.
The five metrics finance teams look at
Simple payback
3.5 – 5.5 yearsNet CapEx ÷ year-one saving. Ignores grid inflation, degradation and time value of money - a rough sanity check, not an investment decision metric.
Discounted payback
4 – 6 yearsSame as simple payback, but future cashflows are discounted (typically at WACC or the corporate hurdle rate). Adds 6–12 months to simple payback.
Internal rate of return (IRR)
18 – 28% (pre-tax)The discount rate at which 25-year cashflows sum to zero. The standard board-level metric for comparing solar against other CapEx projects.
Net present value (NPV) at 8% discount
1.5x – 3x net CapExThe 25-year cash surplus expressed in today's money. Useful for comparing multi-site portfolios where IRRs are similar.
Lifetime unit cost (LCoE)
3.5 – 5p/kWhTotal CapEx + O&M over 25 years, divided by expected 25-year generation. Directly comparable to your grid unit rate.
Worked ROI examples - 100 kWp to 1 MWp
Illustrative benchmarks for standard commercial rooftop systems in the UK in 2026, assuming 70% self-consumption, 26p/kWh blended import rate, 3% annual grid escalation, 0.5% panel degradation and Full Expensing tax relief:
| Size | Gross CapEx | Net after Full Expensing | Y1 generation | Y1 saving | Payback | IRR | 25-yr NPV @8% |
|---|---|---|---|---|---|---|---|
| 100 kWp | £92,000 | £69,000 | 95 MWh | £21,500 | 3.9 yrs | 23% | £185,000 |
| 250 kWp | £205,000 | £154,000 | 238 MWh | £54,000 | 3.5 yrs | 26% | £475,000 |
| 500 kWp | £385,000 | £289,000 | 475 MWh | £108,000 | 3.5 yrs | 27% | £980,000 |
| 1 MWp | £720,000 | £540,000 | 950 MWh | £215,000 | 3.5 yrs | 28% | £2.05m |
Ranges are indicative for a limited company at 25% corporation tax. Use the calculator to plug in your own tariff, roof area and load profile.
Commercial solar ROI by industry
Payback and IRR depend mainly on how much of the generation you use on site. Indicative ranges for well-sized UK systems in 2026:
| Sector | Load profile | Typical payback | Typical IRR |
|---|---|---|---|
| Cold storage & refrigeration | 24/7, high daytime base | 2.5 – 3.5 yrs | 28 – 35% |
| Manufacturing (3-shift) | Continuous | 3 – 4 yrs | 25 – 32% |
| Warehousing & 3PL fulfilment | Long daytime hours | 3.5 – 4.5 yrs | 22 – 28% |
| Agriculture & horticulture | Daytime, seasonal peaks | 4 – 5.5 yrs | 18 – 25% |
| Hotels & leisure | Morning/evening peaks | 4.5 – 6 yrs | 16 – 22% |
| Offices & business parks | Single-shift weekdays | 5 – 7 yrs | 13 – 19% |
| Schools & academies | Term-time daytime | 5 – 7 yrs | 13 – 18% |
Indicative only - your figures depend on tariff, roof and load profile. See our sector pages for warehouses and logistics, factories and manufacturing and cold storage and food production.
Worked example for each industry
One worked example per sector, with the assumptions stated alongside. All figures are indicative only - they illustrate the maths, not a quote for your site. Your tariff, roof, load profile and tax position will move every number.
Cold storage & refrigeration
500 kWp rooftop array on a regional cold store running compressors 24/7
Assumptions
- Gross CapEx £385,000; net £289,000 after Full Expensing (25% corporation tax)
- 475 MWh year-one generation; 95% self-consumption (continuous refrigeration load)
- Blended import rate 27p/kWh; export at 5p/kWh; 3% annual grid escalation; 0.5% degradation
Gross CapEx
£385,000
Year-one saving
£122,000
Simple payback
2.4 yrs
Pre-tax IRR
33%
Round-the-clock cooling load absorbs nearly every kWh generated, which is why cold storage sits at the top of the payback table.
Manufacturing (3-shift)
750 kWp array across two factory roofs on a continuous three-shift operation
Assumptions
- Gross CapEx £540,000; net £405,000 after Full Expensing
- 710 MWh year-one generation; 90% self-consumption
- Blended import rate 26p/kWh; export at 5p/kWh; 3% escalation; 0.5% degradation
Gross CapEx
£540,000
Year-one saving
£170,000
Simple payback
2.8 yrs
Pre-tax IRR
30%
Continuous production means weekend and night-shift generation is still used on site, keeping self-consumption high.
Warehousing & 3PL fulfilment
400 kWp array on a single-shift-plus-overtime distribution warehouse
Assumptions
- Gross CapEx £320,000; net £240,000 after Full Expensing
- 380 MWh year-one generation; 80% self-consumption
- Blended import rate 26p/kWh; export at 5p/kWh; 3% escalation; 0.5% degradation
Gross CapEx
£320,000
Year-one saving
£82,000
Simple payback
3.5 yrs
Pre-tax IRR
25%
Large, unobstructed roofs make warehouses cheap to build on; the main limit is matching array size to a modest daytime base load.
Agriculture & horticulture
250 kWp array on grain stores and livestock buildings at a mixed farm
Assumptions
- Gross CapEx £205,000; net £154,000 after Full Expensing (where the farming business is incorporated)
- 235 MWh year-one generation; 70% self-consumption with seasonal peaks at harvest and drying
- Blended import rate 25p/kWh; export at 5p/kWh; 3% escalation; 0.5% degradation
Gross CapEx
£205,000
Year-one saving
£45,000
Simple payback
4.3 yrs
Pre-tax IRR
21%
Seasonal load means more summer export at the lower export rate; battery storage or load-shifting (grain drying, irrigation) can lift returns.
Hotels & leisure
150 kWp array on a 120-room hotel with laundry, kitchens and pool plant
Assumptions
- Gross CapEx £130,000; net £97,500 after Full Expensing
- 140 MWh year-one generation; 75% self-consumption (morning and evening demand peaks)
- Blended import rate 27p/kWh; export at 5p/kWh; 3% escalation; 0.5% degradation
Gross CapEx
£130,000
Year-one saving
£29,500
Simple payback
4.4 yrs
Pre-tax IRR
20%
Midday solar output lands between the morning and evening peaks; shifting laundry and pool-plant cycles into solar hours is the biggest lever.
Offices & business parks
200 kWp array on a single-shift office building occupied Monday to Friday
Assumptions
- Gross CapEx £160,000; net £120,000 after Full Expensing
- 190 MWh year-one generation; 60% self-consumption (weekend generation exported)
- Blended import rate 26p/kWh; export at 5p/kWh; 3% escalation; 0.5% degradation
Gross CapEx
£160,000
Year-one saving
£32,500
Simple payback
4.9 yrs
Pre-tax IRR
17%
Weekend export at 5p/kWh drags returns; landlord-and-tenant structures or EV charging for staff can absorb more of the weekend output.
Schools & academies
120 kWp array across a secondary school roof, term-time daytime load
Assumptions
- Gross CapEx £100,000, funded from capital or via an on-site PPA (no Full Expensing for most maintained schools; academies should check their own tax position)
- 112 MWh year-one generation; 55% self-consumption (holidays and weekends exported)
- Blended import rate 25p/kWh; export at 5p/kWh; 3% escalation; 0.5% degradation
Gross CapEx
£100,000
Year-one saving
£17,500
Simple payback
5.7 yrs
Pre-tax IRR
15%
The long summer holiday coincides with peak generation, so self-consumption is the lowest of any sector - but the 25-year horizon still clears most trusts' investment criteria.
Indicative only. For figures built on your actual half-hourly data, request a free feasibility review or run the calculator.
Six levers that move ROI most
Self-consumption ratio
Every 10 percentage points of self-consumption typically add 3–5% to project IRR. Load-shifting and battery storage are the two biggest levers.
Grid tariff (import price)
Higher import tariff = higher saving per kWh generated. Sites paying 30p+/kWh see 40%+ IRRs today.
System size
Larger systems get lower £/kWp and better IRRs - but only if self-consumption stays high. Oversizing an array beyond your daytime load pushes IRR down.
Grid price inflation assumption
Modelling flat prices gives conservative IRR. UK grid electricity has risen ~7% CAGR since 2015; using 3–5% escalation is defensible.
Discount rate
Board-level hurdles vary - infrastructure buyers use 6–8%, operating companies use 10–12%, growth SMEs use 15%+. Solar comfortably clears all of these.
O&M cost assumptions
Typical UK commercial O&M runs at 0.5–1% of CapEx/year. Includes annual inspection, cleaning where needed and one inverter replacement at year 12–15.
How solar ROI compares to other CapEx projects
Commercial solar's 20%+ IRRs put it ahead of almost every other operational CapEx category:
| Project type | Typical IRR | Payback |
|---|---|---|
| Commercial rooftop solar | 18–28% | 3.5–5.5 yrs |
| LED lighting retrofit | 25–40% | 1.5–3 yrs |
| Compressor / motor upgrades | 15–25% | 3–5 yrs |
| Voltage optimisation | 10–18% | 4–6 yrs |
| Insulation and building fabric | 8–15% | 6–10 yrs |
| Air-source heat pumps (industrial) | 5–12% | 8–14 yrs |
Sensitivity - what if grid prices fall 25%?
A common board question. Even with UK non-domestic electricity falling from ~26p to ~20p/kWh blended (a 23% fall), a 500 kWp array on a 70%-self-consumption site would move from ~£108k year-one saving to ~£83k, extending simple payback from 3.5 to ~4.6 years and dropping IRR from ~27% to ~19% - still comfortably above most corporate hurdle rates. Every credible UK forecast has non-domestic prices staying well above 2019 levels through 2035.
Related reading
FAQ - commercial solar ROI and payback
What is the ROI on business solar panels?
For a UK business in 2026, a well-sized commercial solar array typically returns its cost in 3.5–5.5 years and then generates effectively free electricity for another 20+ years. In investment terms that is a pre-tax IRR of 18–28% and a 25-year net present value of 1.5x to 3x the net capital cost at an 8% discount rate. Businesses with high daytime usage - cold storage, manufacturing, fulfilment - sit at the top of those ranges.
What is the ROI on commercial solar panels in the UK?
A well-sized UK commercial solar array typically delivers a pre-tax IRR of 18–28% over 25 years, with simple payback of 3.5–5.5 years after Full Expensing. Net present value at an 8% discount rate is usually 1.5x to 3x the net CapEx. Larger systems on high-consumption sites sit at the top of these ranges.
What is the payback period for commercial solar in the UK?
In 2026, most UK commercial solar arrays pay back in 3.5–5.5 years. Payback is driven mainly by self-consumption ratio and grid import price. Sites with 24/7 refrigeration, continuous manufacturing or 3PL fulfilment often pay back in under 4 years; single-shift office estates sit at 6–7 years.
Is commercial solar a good investment for UK businesses in 2026?
Yes. Panel prices are 40% lower than 2022, grid electricity remains 60–80% above pre-2021 levels, and Full Expensing gives limited companies 25p back per £1 of CapEx. The combination pushes typical project IRRs into the mid-20s - comfortably above almost every corporate hurdle rate.
How is commercial solar ROI calculated?
Take annual saving (self-consumed kWh × grid unit rate + exported kWh × export rate), subtract O&M, project it over 25 years with 0.5% annual panel degradation and an assumed grid tariff escalation. Discount future cashflows at your corporate hurdle rate to get NPV. Divide net CapEx by year-one saving for simple payback.
What is the IRR of commercial solar in the UK?
UK commercial solar delivers a typical pre-tax IRR of 18–28% over 25 years. Post-tax IRR (after 25% corporation tax on savings but including Full Expensing on CapEx) is typically 14–22%. This clears every mainstream corporate hurdle rate.
How long do commercial solar panels take to pay back after tax?
For limited companies, Full Expensing effectively knocks 25% off the sticker CapEx in year one. Combined with 2026 grid prices, post-tax simple payback is typically 3.5–5 years for a well-sized commercial array. Cold storage, 24/7 fulfilment and continuous manufacturing sites can achieve sub-3-year post-tax payback.
What discount rate should I use for a commercial solar business case?
Use your corporate WACC or the hurdle rate finance uses for other CapEx projects. UK infrastructure buyers typically use 6–8%; trading companies use 10–12%; growth SMEs use 15%+. Solar comfortably delivers positive NPV at all of these rates - the choice of discount rate mainly affects the size of the NPV, not the go/no-go decision.
Does commercial solar still make ROI sense if grid prices fall?
Yes. Even at a 25% fall in UK non-domestic electricity prices (to ~20p/kWh blended), typical commercial solar arrays still return 6–8 year payback and 12–15% IRR - still comfortably ahead of most corporate hurdles. Every credible UK forecast has prices staying well above 2019 levels through 2035.
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