Commercial Solar ROI: UK Payback, IRR & 25-Year Returns
UK commercial solar delivers a 15-25% IRR and pays back in 4-7 years — or 3-4.5 years after Annual Investment Allowance tax relief. See ROI by system size, region and scenario, with worked examples.
Quick Answer
What is the payback period and ROI on commercial solar?
UK commercial solar typically pays back in 4-7 years on a cash purchase, or 3-4.5 years after Annual Investment Allowance tax relief. It delivers an IRR of 15-25% and a 25-year net return of roughly 5-8x the net cost. A 100kWp system costing ~£90,000 (~£67,500 net after AIA) saves ~£18,700/year — a post-AIA payback of about 3.6 years.
4-7 yrs
Simple Payback
3-4.5 yrs
Post-AIA Payback
15-25%
Typical IRR
5-8x
25-Year Net Return
What Is ROI on Commercial Solar?
"Return on investment" for commercial solar is measured four ways — it's worth being clear which one a number refers to:
- Payback period — the time for cumulative savings to equal the net system cost. UK commercial solar: 4-7 years simple, 3-4.5 years after AIA tax relief.
- Lifetime savings — cumulative £ saved over the 25-30 year system life, typically £450,000-£720,000 for a 100kWp system.
- Lifetime ROI % — total return as a percentage of net cost, commonly 600-1,000% over the system life.
- Annualised return / IRR — the internal rate of return accounting for the time value of money: 15-25% for UK commercial solar, comfortably ahead of commercial property (5-8%) or long-run equities (7-10%).
How to Calculate Commercial Solar Payback & ROI
The formulas
Simple payback (years) = Net system cost (after AIA relief) ÷ (annual self-consumption savings + annual SEG export income)
Lifetime ROI (%) = (lifetime net benefit − net cost) ÷ net cost × 100
Three inputs drive the result: the net cost of the system (after the Annual Investment Allowance returns ~25% of the cost as a first-year corporation-tax saving), the annual savings from electricity you self-consume, and the income from electricity exported under the Smart Export Guarantee (8-20p/kWh).
Worked Example: 100kWp System
- Installed cost: ~£90,000 (at ~£0.90/W)
- AIA first-year tax relief: ~25% cash benefit at 25% CT = −£22,500
- Net effective cost: ~£67,500
- Annual generation: ~95,000 kWh
- Annual benefit: 65% self-consumed @ 30p + 35% exported @ 12p SEG = ~£18,700/year
- Post-AIA payback: £67,500 ÷ £18,700 = ~3.6 years
Illustrative; actual figures vary by site, tariff and usage.
Payback Period by System Size
Larger systems benefit from economies of scale, achieving faster payback and higher IRR. Net cost is after 25% AIA corporation-tax relief; figures assume 30p/kWh, 65% self-consumption, 12p/kWh SEG.
| System Size | Installed Cost | Net Cost (post-AIA) | Annual Benefit | Payback (post-AIA) | 25yr Net Return |
|---|---|---|---|---|---|
| 30kWp | ~£27,000 | ~£20,250 | ~£5,600 | 3.6 yrs | ~£140,000 |
| 50kWp | ~£45,000 | ~£33,750 | ~£9,400 | 3.6 yrs | ~£235,000 |
| 100kWp | £75k-£105k | ~£67,500 | ~£18,700 | 3.6 yrs | ~£470,000 |
| 250kWp | £180k-£230k | ~£157,500 | ~£46,800 | 3.4 yrs | ~£1.18m |
| 500kWp | £350k-£425k | ~£300,000 | ~£93,500 | 3.2 yrs | ~£2.35m |
Systems exporting 50kWp+ require a G99 connection. Illustrative — actual results vary by location, roof and usage.
Payback Period by UK Region
Solar irradiance varies across the UK — southern regions receive ~15-20% more solar radiation than the north, shortening payback. Based on a 100kWp system, 30p/kWh, 65% self-consumption, post-AIA.
| Region | Yield (kWh/kWp/yr) | Annual Generation | Payback (post-AIA) | 25yr ROI |
|---|---|---|---|---|
| South West / South East | ~1,000 | ~100,000 kWh | 3.4 yrs | ~720% |
| Midlands / East | ~950 | ~95,000 kWh | 3.6 yrs | ~700% |
| North / NW | ~880 | ~88,000 kWh | 3.9 yrs | ~640% |
| Scotland | ~800 | ~80,000 kWh | 4.2 yrs | ~590% |
Sensitivity Analysis: 100kWp System
How changes in electricity price and self-consumption affect payback and return, for a 100kWp system at ~£90,000 installed (~£67,500 net after AIA).
| Scenario | Electricity Price | Self-Consumption | Annual Benefit | Payback | IRR |
|---|---|---|---|---|---|
| Conservative | 20p/kWh | 50% | ~£12,300 | 5.5 yrs | ~15% |
| Base case | 30p/kWh | 65% | ~£18,700 | 3.6 yrs | ~20% |
| Optimistic | 40p/kWh | 80% | ~£26,500 | 2.5 yrs | ~25%+ |
Factors That Affect Your Payback Period
- Electricity price — the biggest lever. Every kWh self-consumed is worth your full day-rate (20-40p), so high tariffs slash payback.
- Self-consumption ratio — daytime-operating businesses self-consume 65-85% of generation; adding battery storage pushes this to 85-90%.
- System size — larger systems cost less per kWp, improving IRR.
- Region & roof orientation — south-facing, unshaded roofs in southern England yield most.
- AIA & finance — the Annual Investment Allowance returns ~25% of cost as year-1 tax relief; finance/PPA spreads cost so the system is cash-positive from day one.
- SEG export rate — surplus exported at 8-20p/kWh adds income on top of self-consumption savings.
Solar ROI vs Other Business Investments
| Investment | Typical Annual Return | Notes |
|---|---|---|
| Commercial solar | 15-25% IRR | Inflation-hedged, AIA tax-advantaged |
| Commercial property | 5-8% | Illiquid, management overhead |
| Equities (long-run) | 7-10% | Volatile, no tax relief |
| Cash / deposits | ~4-5% | Eroded by inflation |
Related Resources
- Commercial solar cost guide — £/W and £/kWp by system size
- Capital allowances & AIA guide — how the tax relief works
- Commercial solar calculator — model your savings
- Solar financing & PPA — zero-capital routes
- Get a free ROI analysis — tailored 25-year model
Frequently Asked Questions
How long is the payback period on commercial solar in the UK?
UK commercial solar typically pays back in 4-7 years on a cash purchase, or 3-4.5 years after claiming the Annual Investment Allowance. Payback depends most on your electricity price and self-consumption ratio — a business paying 30p+/kWh with high daytime usage sits at the faster end.
What is a good ROI or IRR for commercial solar?
Commercial solar in the UK delivers an internal rate of return (IRR) of 15-25%, well ahead of commercial property (5-8%) or long-run equities (7-10%). Over the 25-year system life, the net return is typically 5-8x the net cost — a lifetime ROI of 600-1,000%.
How does the Annual Investment Allowance affect payback?
The AIA gives a 100% first-year capital deduction on the system cost, which at the 25% corporation-tax rate returns about 25% of the cost as a cash tax saving in year one. On a £90,000 system that's ~£22,500, cutting the net cost to ~£67,500 and shortening payback by roughly 12-18 months.
Does the Smart Export Guarantee shorten payback?
Yes. Electricity you don't use on site is exported and paid for under the Smart Export Guarantee at 8-20p/kWh depending on the tariff. For a typical commercial system exporting 30-40% of generation, SEG adds several thousand pounds of annual income on top of self-consumption savings.
Does battery storage change the payback period?
Battery storage raises self-consumption from ~65% to 85-90% by shifting surplus daytime generation into evening use, increasing annual savings. It adds £400-£600/kWh to the project, so it typically adds 1-2 years to payback on its own but improves total lifetime return — most valuable where day-rates are high or export rates low.
How does region affect commercial solar payback?
Southern England receives ~15-20% more solar irradiance than the north (≈1,000 vs ≈880 kWh/kWp/year), so a southern system generates more and pays back a little faster (~3.4 vs ~3.9 years post-AIA for 100kWp). Even Scotland at ~800 kWh/kWp pays back within ~4.2 years post-AIA.
Can I get a return with no upfront cost?
Yes. Asset finance or leasing spreads the cost so monthly repayments are usually lower than the energy savings, making the system cash-positive from month one. A Power Purchase Agreement (PPA) involves zero capital — a funder owns the system and you buy the power at below grid price. See our commercial solar financing guide.
What happens after the payback period?
Once the system has paid for itself (year 3-5), every unit it generates for the remaining 20+ years is effectively free. Modern panels retain 80-85% of output at year 25, so a system installed in 2026 keeps generating low-cost electricity into the 2050s — the bulk of the lifetime return accrues after payback.
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Commercial Solar Payback Period by Sector — 2026 Data
Payback periods vary significantly by sector due to differences in daytime electricity consumption patterns, system size, and energy tariff levels:
| Sector | Typical System Size | Pre-AIA Payback | Post-AIA Payback | Key Driver |
|---|---|---|---|---|
| Cold storage / refrigeration | 100–500kWp | 3.2–4.5yr | 2.4–3.4yr | 24/7 base load |
| Food manufacturing | 100–300kWp | 3.0–4.2yr | 2.3–3.2yr | High daytime load |
| Warehousing / logistics | 150–500kWp | 3.5–5.0yr | 2.6–3.8yr | Large roof area |
| Manufacturing / industrial | 50–200kWp | 3.0–4.5yr | 2.3–3.4yr | Shift patterns |
| Office buildings | 30–100kWp | 5.0–7.0yr | 3.8–5.3yr | Weekend/evening drop |
| Schools / colleges | 30–150kWp | 4.5–6.5yr | 3.4–4.9yr | Holiday periods |
| Farms | 30–200kWp | 3.0–5.0yr | 2.3–3.8yr | FETF grants + AIA |
How Electricity Tariff Affects Commercial Solar Payback
Your electricity tariff is the single most important variable in commercial solar payback. The higher your tariff, the faster your payback:
| Electricity Tariff | Annual Saving (100kWp) | Pre-AIA Payback | Post-AIA Payback |
|---|---|---|---|
| 24p/kWh | ~£20,200 | 4.6yr | 3.4yr |
| 27p/kWh | ~£22,700 | 4.1yr | 3.1yr |
| 29p/kWh (2026 avg) | ~£24,400 | 3.8yr | 2.9yr |
| 32p/kWh | ~£26,900 | 3.5yr | 2.6yr |
| 36p/kWh | ~£30,200 | 3.1yr | 2.3yr |
Based on a 100kWp system generating 83,000 kWh/year (Midlands irradiance), costing £91,500 all-in. Post-AIA assumes 25% CT rate with 100% AIA claimed in Year 1.