Interactive Tool

Commercial solar finance calculator

Indicative comparison of capital purchase, green loan, operating lease, finance lease, and PPA across your project numbers — including battery storage and AIA-vs-FYA tax routes. Updates live as you change inputs.

For first-pass screening. Real project economics depend on lender pricing, site conditions, and your specific tax position. Use this to short-list structures, then request a full advisory review on the top candidates.

Your project

Adds £450/kWh capex. Models 350 cycles/year at 90% round-trip efficiency.

Updates as you type. No data sent anywhere — calculation runs in your browser.

Indicative results

Five finance structures across your project numbers. Year 1 includes capex outflow, electricity savings, export revenue, battery contribution where included, and the corporation tax effect of the selected allowance route.

Annual generation— MWh
Year-1 saving£—
£/kWp solar£—

Caveats and assumptions

  • Green loan: 7-year term at 7% APR.
  • Operating lease: 8-year term at implicit ~8% APR with lessor margin. No FYA capture.
  • Finance lease: 8-year term at 7.5% APR. FYA captured by lessee.
  • PPA: 20-year term at 16p/kWh consumed. No capex.
  • Export revenue: 7p/kWh on solar generation not self-consumed and not absorbed by battery.
  • Battery: £450/kWh usable capex; 350 cycles/year at 90% round-trip efficiency; replacement at year 14 (60% of original capex).
  • 25-year cumulative includes 1.5% real tariff inflation, inverter replacement at year 12 (£100/kWp), £10/kWp/year O&M.
  • AIA route: 100% × tax rate on full capex year 1 (capped at £1m AIA cap — calculator does NOT enforce the cap).
  • FYA route: 50% × tax rate year 1; remaining 50% in special-rate pool at 6% writing-down.

Calculator FAQs

How accurate are the calculator outputs?
The calculator produces indicative numbers based on representative 2026 UK market parameters: 950 kWh/kWp/year typical generation, 7p/kWh export tariff, 7% APR green loan, 8% APR operating lease, £450/kWh usable battery capex. Real project economics depend on specific site conditions, lender pricing on the day, and your tax position — typically within ±15% of indicative. The calculator is for first-pass screening; we always model your actual numbers in the formal review.
How does the AIA toggle change results?
The Annual Investment Allowance gives 100% deduction in year one on the first £1m of qualifying capital expenditure per accounting period. Where you have AIA headroom available, AIA delivers stronger year-one tax relief than the 50% FYA route — for a £200k system at 25% main rate, AIA saves £50k year-one vs £25k via FYA. AIA wins where it's available; FYA fills in where AIA headroom is exhausted. Set "Tax allowance" to "AIA" if you have remaining AIA headroom for the period.
How is battery storage modelled?
Battery contribution is computed as: kWh capacity × 350 cycles/year × 90% round-trip efficiency × tariff differential (avoided cost minus export tariff). On a typical 100kWh battery with 15p/kWh differential, that's roughly £4,725/year of additional saving from time-shifted self-consumption and avoided export curtailment. Capex assumes £450/kWh usable. The model excludes capacity-market and FFR revenue (which require aggregator partnerships) and time-of-use peak/off-peak arbitrage (which depends on specific tariff structure).
What corporation tax rate does the calculator assume?
It defaults to 25% (the 2026 main rate for companies with profits above £250,000). Companies with profits between £50k and £250k pay 19–25% on a marginal scale; companies under £50k pay 19%. The tax allowance value scales linearly — at 19% the £200k system saves £19k year-one via FYA (vs £25k at 25%).
Can I share the calculator with these specific inputs?
Yes — click the "Share this calculation" button. The URL is updated to include all your inputs as parameters; copying it lets a colleague open the calculator pre-filled with your numbers. Useful for sharing with the rest of the project team or with us when requesting a formal review.

Ready for the formal model?

The calculator gives you the shape. The formal advisory review pulls in your actual half-hourly demand, current accounting position, competitive lender pricing, and the specific tax-allowance position based on your full year capex profile. Five working days from enquiry to indicative comparison.

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