Capital Purchase for Commercial Solar
Pay cash, own the asset, claim the full tax relief — the simplest structure and almost always the most economic over 25 years.
Indefinite — system life of 25–30 years
100% upfront capital, no financing cost. Total cost of ownership lowest of any structure.
Typically 14% to 22% pre-tax IRR depending on self-consumption, electricity rate, and irradiance.
How it works
Capital purchase is the simplest commercial solar finance structure: you pay for the system in full, you own it, you depreciate it, you claim the capital allowances, and you keep every kWh of electricity it generates. The case for capital purchase rests on three numbers — the avoided electricity cost (which falls straight to the bottom line at zero marginal cost from year two onward), the corporation tax relief on the capital cost, and the residual asset value at year 25. For a profitable trading company paying corporation tax at the main rate, the 50% First Year Allowance turns a £200,000 system into a net £175,000 outlay in year one. Add the AIA where headroom remains, and the effective cost falls further. Over 25 years, no other finance structure beats capital purchase on total cost — every £1 of finance cost added to the project is £1 less of return. The reason businesses sometimes choose another structure isn't economic, it's about constraints: capex limits, balance sheet preferences, or tax position. Where capital is available and the business is profitable, capital purchase is the default.
Worked example: 250kWp on a £200,000 commercial system
£200,000 (250kWp at £800/kWp installed)
£200k outflow + £25k corp tax saved on FYA = £175k net year-one cost. Plus ~£42k year-one electricity saving (250kWp generating ~245MWh × ~17p/kWh blended). Net year-one cash position: -£133k.
+£1.4m to +£1.8m cumulative free cash flow (electricity savings net of inverter replacement at year 12, O&M, and modest electricity inflation).
Typically 14% to 22% pre-tax IRR depending on self-consumption, electricity rate, and irradiance.
Strongest economics. Payback typically 3.5–5 years simple, sub-3 years post-FYA for profitable companies.
Best fit
- ● Profitable corporation-tax-paying companies with available cash
- ● Long-tenanted commercial property owners
- ● Public-sector bodies with capital budget
- ● Family-owned businesses prioritising lifetime cost over balance sheet
Not suitable for
- ○ Companies with binding capex constraints
- ○ Loss-making businesses (FYA has no immediate value if no profits to offset)
- ○ Tenanted commercial property without lease-length certainty
Pros
- Lowest total cost of ownership over 25 years
- Full FYA + AIA benefits go to the buyer
- Asset on balance sheet supports future borrowing capacity
- Complete control of system, monitoring, and any future expansion
- All export revenue and SEG income retained
- No counterparty risk — no third-party in the structure
Cons
- Requires £150k–£500k+ capital outlay for typical commercial systems
- Capital tied up in solar rather than core business
- Buyer carries inverter replacement and O&M responsibility (£80–£120 per kWp around year 12)
- Tax relief value depends on having profits to offset
Mechanics
Ownership model
Buyer takes legal title to the system on commissioning. The asset sits on balance sheet and depreciates over its useful life (typically 25–30 years for accounting purposes).
Balance sheet treatment
Asset added to fixed assets at cost. Depreciation charged annually through P&L. The system is a tangible asset that can support secured borrowing if needed later.
Tax treatment
Eligible for 50% First Year Allowance on the qualifying capital cost (extended to 31 March 2026), with the remaining 50% added to the special-rate capital allowance pool at 6% writing-down allowances. Annual Investment Allowance (AIA) may also be available at 100% in year one for the first £1m of qualifying spend if not yet claimed against other expenditure. Operating costs deductible in the year incurred.
Who offers it
Direct from installer. We assemble the case and source competitive turnkey pricing.
Compare with other finance routes
Green Loans
Borrow against the project, retain ownership, smooth the cash impact — green loans typically charge 6–9% APR for solar specifically.
Operating Lease
The leasing company owns the system; you pay a fixed annual rent. Off-balance-sheet, fully expensable, but you don't get the FYA.
Finance Lease
Functionally similar to a loan — you pay over time, the asset hits your balance sheet, and you keep the tax benefits, but with leasing-company structure.
Direct comparisons
Frequently asked questions
Why is capital purchase typically the strongest commercial solar finance route?
How much capital do I need for commercial solar capital purchase?
When does capital purchase NOT make sense?
Can capital purchase combine with green loan financing?
Do tax allowances apply to capital purchase if I lose money this year?
Capital purchase for commercial solar — detailed guide
Outright capital purchase — funding a commercial solar installation from the company's own resources — remains the structurally optimal choice for profitable UK businesses with sufficient capital reserves and a 25% corporation tax rate. The combination of FYA (50% tax relief in year 1), immediate elimination of a significant electricity cost, and 25-year asset life produces unlevered IRRs typically in the range of 15–22% for well-specified UK commercial solar installations.
Why capital purchase beats financed alternatives — for the right buyer
| Metric | Capital purchase | HP (8.5% APR, 5yr) | Operating lease | PPA |
|---|---|---|---|---|
| Total cost of capital (£500k system, 25yr) | £500,000 + opportunity cost | £627,000 (total payments) | £675,000+ (20yr rentals) | £0 capital + contracted electricity cost |
| Year-1 net cash position | +£104,000 saving - £500k outlay + £62,500 FYA CT relief = net -£333,500 | +£104,000 - £73,200 HP + £37,500 FYA CT = +£68,300 | +£60,000 net (saving minus lease) | Positive from day 1 |
| 25-year NPV (5% discount rate) | Highest — no finance cost | Second — finance cost reduces NPV by £80-120k | Third — implicit interest cost | Lowest — developer takes margin |
| Balance sheet impact | Asset capitalised; equity increases | Asset + liability capitalised | Off-balance-sheet (FRS 102/IFRS16 conditions) | No impact |
| Tax benefit | Full 50% FYA year 1 | Full 50% FYA year 1 (HP) | Rental deductible; no capital allowances | Electricity cost (expense) only |
For a business with £1m+ in free cash reserves and a clear 25% CT rate, capital purchase produces the best after-tax 25-year outcome. The opportunity cost of deploying capital into solar (at 15–22% IRR) should be compared against alternative uses — for most businesses, solar outperforms cash deposits, bond funds, or incremental working capital investment.
Phased capital deployment
Businesses with sufficient capital but hesitant to deploy all at once can structure a phased programme — installing in tranches over 2–3 years. This approach:
Benefits of phased deployment
Spreads capital commitment across tax years (multiple FYA claims); allows performance validation of the first installation before committing to subsequent phases; permits system design refinement based on actual generation data from phase 1. Installers typically offer a pricing framework for phased programmes — securing the unit cost at phase 1 pricing for future tranches.
Risks of phased deployment
Equipment prices may change between phases (historically trending down, but supply chain disruptions in 2022–23 demonstrated price volatility). If electricity prices fall materially between phases, the ROI case for later phases weakens (though historically unlikely over a 2-3 year horizon). Phase 1 installer quality should be confirmed before committing to the same contractor for phase 2.
How to evaluate the capital purchase business case
A rigorous capital purchase business case should include the following components:
Year-by-year cash flow model (25 years)
Show: annual generation (using P90 yield, degraded at 0.5%/year), avoided electricity cost (using a conservative 3% p.a. electricity price escalation rate), annual O&M cost (typically £6–10/kWp/year), inverter replacement reserve (one replacement at year 12–15, budget £8,000–30,000 depending on system size), and annual tax effect (FYA year 1, main pool WDA years 2+). Discount all cash flows at the business's weighted average cost of capital (WACC) or hurdle rate to produce the NPV.
Sensitivity analysis
Key sensitivities to show: electricity price escalation (+/-1% per year), system yield (P90 vs P50 vs P10), capital cost (±10%), and corporate tax rate changes. A project that is strongly NPV-positive under P90 assumptions and a conservative 2% electricity price escalation passes the basic "what could go wrong" test for capital committee approval.
Benchmarking against alternative uses of capital
The capital committee will want to understand: what else could this £500k be used for? Compare the solar IRR against: leaving the capital in cash/money market funds (current rate ~5.0%); paying down existing debt (if debt is at 7%+, paying it off is equivalent to a risk-free 7% return — difficult for solar to beat on a risk-adjusted basis); or investing in production capacity / marketing (compare IRR against the business's standard hurdle rate, typically 12–20% for commercial decisions).
AIA vs 50% FYA: choosing the right capital allowance for commercial solar
Capital purchase for commercial solar gives you a choice of two accelerated capital allowance routes in 2026, and the wrong choice can cost you 6–8% of the system cost in real terms. Annual Investment Allowance (AIA) gives 100% relief in year one up to £1m. The 50% First Year Allowance (FYA) under full expensing gives 50% in year one followed by 25% WDA each subsequent year. For most commercial solar installations, AIA is more efficient — but there are scenarios where FYA is the right answer.
| Scenario | Best route | Why |
|---|---|---|
| System cost under £1m, company has unused AIA headroom | AIA (100% in year one) | Full relief in year one maximises NPV of tax benefit; straightforward HMRC treatment |
| System cost over £1m | AIA on first £1m + FYA on balance | Split approach recovers maximum relief in year one on the largest asset |
| Company is in a tax loss position in year one | FYA (spread relief) | 50% FYA in year one, 25% WDA rolling — relief better matched to when taxable profits exist |
| System purchased in final month of accounting period | AIA preferred | AIA is all or nothing in the period; FYA may be better if only 1 month of profit available to absorb relief |
| Capital purchased via HP agreement | AIA or FYA via HP — same treatment | CA relief available to the HP purchaser from first day of use, not from final payment |
Capital purchase financial model: £200k commercial solar system
The worked example below shows a 200kWp system for a manufacturing business paying 25% corporation tax. Energy savings are modelled at 35p/kWh (2026 commercial tariff) with 4% annual escalation. AIA claimed in full in year one.
| Year | Capital outlay | AIA / FYA tax relief | Energy saving | Net cash position | Cumulative |
|---|---|---|---|---|---|
| Year 0 (purchase) | −£200,000 | +£50,000 (AIA @ 25% CT) | — | −£150,000 | −£150,000 |
| Year 1 | — | — | +£27,300 | +£27,300 | −£122,700 |
| Year 2 | — | — | +£28,392 | +£28,392 | −£94,308 |
| Year 3 | — | — | +£29,528 | +£29,528 | −£64,780 |
| Year 4 | — | — | +£30,709 | +£30,709 | −£34,071 |
| Year 5 | — | — | +£31,937 | +£31,937 | −£2,134 |
| Year 6 | — | — | +£33,215 | +£33,215 | +£31,081 |
| Year 7–25 | — | — | Escalating | Compounding | +£600k+ over 25 years |
Real payback is 5.0–5.5 years on capital purchase for most manufacturing and logistics businesses
The model above shows a 5–6 year simple payback for a 200kWp manufacturing facility buying outright. The AIA tax relief in year one reduces the effective capital outlay from £200,000 to £150,000 (assuming the company has sufficient taxable profit to absorb the full AIA claim). In energy terms, 200kWp at full capacity generates approximately 180,000–200,000 kWh/year in the UK, saving £63,000–£70,000/year at 35p/kWh in 2026. Combine tax relief, energy saving, and SEG export income and the economics are compelling for any business with stable energy consumption and a long property tenure.
Capital purchase vs green loan vs PPA: 25-year total cost comparison
| Finance route | Day-one outlay | Annual cost (years 1–10) | Annual benefit (years 11–25) | 25-year total net benefit | Best for |
|---|---|---|---|---|---|
| Capital purchase (AIA year 1) | £200,000 (net £150k after tax) | −£200k funded; +£27–50k/yr energy/SEG | +£35–75k/yr (fully owned) | £600k–£900k | Companies with capital and high CT; long property tenure |
| Green loan (6.5%, 7 years) | £0 | Loan repayment −£27k/yr offset by +£27–35k savings — near neutral | +£35–75k/yr (owned at loan end) | £400k–£700k | Growing businesses preserving working capital; still want ownership |
| Operating lease (10 years) | £0 | +£10–20k/yr net saving vs bills | System returned at end; new deal needed | £150k–£300k | Short tenure; off-balance-sheet requirement; public sector |
| PPA (15–25 year, 8p/kWh) | £0 | +£10–25k/yr vs grid (escalating) | No ownership benefit; ongoing PPA rate | £200k–£400k | Businesses that want simplicity; cannot access capital or loans |
HMRC compliance for commercial solar capital allowances
HMRC has specific requirements for commercial solar capital allowance claims. Errors in how the claim is presented in your company tax return (CT600) can delay relief or trigger an enquiry. The key compliance points are:
Qualifying conditions for AIA and FYA on commercial solar
(1) The asset must be “plant and machinery” under Capital Allowances Act 2001 — commercial solar PV qualifies as main pool P&M. (2) The business must use the asset in a qualifying activity (trade, profession, or vocation). (3) AIA is available in the period the expenditure is incurred — not when the invoice is paid. (4) For FYA full expensing, the company must be subject to corporation tax (not income tax); sole traders and partnerships do not qualify for full expensing and must use AIA. (5) The AIA pool limit of £1m applies across all P&M expenditure in the year, not just solar — check total capital spend before assuming full £1m is available for the solar claim.
Selling the building after claiming AIA: the balancing charge risk
If you claim AIA in year one and sell the property (and system) within 5–7 years, HMRC may raise a balancing charge — a tax bill that claws back some of the upfront relief. The balancing charge equals the sale proceeds attributed to the solar system less the tax written-down value (which is zero after a full AIA claim). This is a real risk for property investment businesses or any company that might sell the freehold within 5–7 years of installing solar. A finance lease or green loan (where the lender claims the CAs) avoids this exposure entirely.
Model Capital alongside the alternatives
We build a side-by-side after-tax comparison across all six structures using your actual numbers — not lender brochure assumptions.
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