How Much Could Solar Save You?
Enter your building size and monthly electricity bill. Our calculator estimates your system size, payback period, and 25-year return in under 30 seconds.
Solar ROI Calculator
Enter your building size and monthly electricity bill for a personalised savings estimate for any UK commercial building.
Your Building Details
Include total footprint of available roof, car park, or ground space.
Your most recent commercial electricity bill (excluding VAT and CCL if possible).
This is a simplified estimate based on UK averages. A proper survey uses half-hourly consumption data, shading analysis, and structural assessment to give you an accurate proposal.
Enter your details to see results
Add your building area and monthly bill above. We will estimate system size, annual savings, and payback instantly.
How the Estimate Works
We use UK-average solar irradiance, typical commercial installation costs, and your inputs to build a realistic first-pass financial model.
Enter Your Building
Tell us your available roof or ground area and average monthly electricity bill. The calculator works for warehouses, factories, offices, farms, and more.
We Size Your System
Using your area and bill, we estimate the maximum kWp that fits both physically and financially. You can tweak self-consumption and grid rates for a closer match.
See Your Return
Get annual savings, payback years, CO₂ offset, and a full 25-year cumulative return chart. Download a PDF to share with your finance director.
This is a starting point — not a final quote.
The calculator uses UK-average assumptions. Your actual savings depend on shading, roof orientation, structural capacity, grid connection, and half-hourly consumption patterns. For an accurate proposal, book a free site survey — we will model everything with real data.
What a real survey covers
- Half-hourly consumption profile analysis
- Drone-based shading and roof condition survey
- Structural load assessment by chartered engineer
- Grid connection capacity and DNO application
- Bespoke financial model with actual unit rates
- Planning and heritage impact assessment if needed
Common Questions
Quick answers about how the calculator works and what comes next.
How accurate is this estimate?
It is accurate to within ±20% for most commercial buildings in the UK, assuming a south-facing unshaded roof and typical electricity rates. Shading, roof orientation, and structural constraints can shift the numbers. The survey refines everything.
Why does the calculator need my roof area AND my bill?
Roof area tells us the maximum system size that fits physically. Your bill tells us the maximum that makes financial sense — there is no point installing more capacity than you can consume or export profitably. We take the lower of the two.
What is self-consumption and why does it matter?
Self-consumption is the percentage of solar generation you use on-site rather than exporting to the grid. The higher it is, the better your return, because grid electricity costs ~£0.32/kWh while export pays only ~£0.12/kWh under SEG tariffs.
Does the calculator include battery storage?
Not directly. The calculator models solar-only savings. If you are interested in battery storage, mention it when you book a survey — we will model the additional peak-demand savings and backup benefits separately.
Can I save my results and come back later?
Yes — your inputs are saved automatically in your browser. If you close the page and return, your numbers will still be there. You can also download a PDF summary to share with colleagues.