📊 Financial & Technical Modeler

Commercial Solar Sizing & ROI Calculator

Explore indicative system capacity (kWp), annual electricity value (£) and simple gross-cost payback for your UK premises. Enter your own avoidable import and potential export rates; tax relief is not assumed.

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Vetted UK Commercial EPC Installation Network

Our commercial installation partners are rigorously vetted and accredited to the UK's highest technical, electrical, and site-safety standards:

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SafeContractor

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Quality & Environment

Solar Energy UK

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Microgeneration Standards

Vetted Commercial Partner

Butterfly Eco

Commercial solar PV, LED lighting and EV charging specialists. Zero-capital Solar as a Service, direct Capex, and sector-specific delivery for businesses, schools and care homes.

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Interactive Sizing

Facility Parameters

Live Desk Estimate

Premises Sector

Average Monthly Electricity Spend£3,500 / mo

£1,000£10,000£20,000£30,000+

Estimated Usable Roof / Land Area15,000 sq ft

3,000 sq ft25,000 sq ft50,000 sq ft80,000+ sq ft

Operating Hours Profile

Avoidable grid unit rate (p/kWh)Agreed export rate (p/kWh)

Enter the import charges solar would actually avoid and your agreed export rate, or 0 if no export income is expected. Without both figures, financial results are withheld. Check your bills and contract.

Desk Yield Model

Indicative Financial Returns

Self-Cons: 75%

Indicative System Sizing105 kWp~236 Tier-1 Panels

Indicative Annual Electricity ValueEnter your rates/ year: modelled import avoidance plus potential export income

Est. Annual Generation:94,500 kWh / yr

Est. Turnkey Capex:£63,000

Simple payback on gross estimated cost:Enter your rates

Excludes tax relief, financing, maintenance, roof works, grid costs and changes in generation or tariffs. For conditional tax scenarios, use the capital allowances guide.

Calculation Methodology & Engineering Assumptions

1. Solar yield: The desk model assumes 900 kWh per kWp each year, approximately 60 sq ft of usable area per kWp and illustrative sector-based costs and self-consumption. Actual yield, usable roof area, demand matching and installed cost need a site assessment.

2. Electricity value: Annual value is modelled self-consumed kWh × your avoidable grid rate, plus potential exported kWh × your entered export rate. No tariff is assumed by default; export permission and half-hourly demand may change the outcome.

3. Simple payback: Estimated gross installed cost divided by the indicative annual electricity value, with no assumed tax relief. This excludes financing, maintenance, roof works, connection costs, generation degradation and future price changes. See the capital allowances guide for a separate conditional tax illustration.

Calculator FAQs

Frequently Asked Questions

How does the commercial solar calculator estimate system sizing?

The model uses your monthly spend, estimated usable roof area and a broad sector profile to suggest capacity. Its 60 sq ft per kWp area rule and self-consumption percentages are illustrative, not an engineered roof layout or half-hourly demand forecast.

Which electricity rates should I enter?

Enter the import unit charges that on-site generation would actually avoid and an export rate you could secure, or zero if you expect no export income. No rates are pre-filled; without both figures, the calculator withholds financial results. Fixed bill charges may not be avoidable.

Does simple payback include AIA tax relief?

No. Payback divides estimated upfront system cost by indicative annual import avoidance plus potential export income. It does not assume any tax saving. AIA eligibility, remaining allowance and the actual tax effect depend on the buyer, asset and accounting period; review the capital allowances guide with a tax adviser.

Is this calculator estimate an official quote?

No. The result is a simplified desk illustration, not an installation quote or network approval. Ask a qualified designer to assess roof structure, site demand and the applicable DNO connection process before making an investment decision.