Two homes with the same number of panels can see different savings. A forecast is most useful when it reflects your property and shows the assumptions behind the result.
Start with annual generation
Panel capacity is only one part of the picture. Location, orientation, pitch, shading and system losses influence annual output. Winter and summer production can be very different.
Then look at when you use energy
Electricity used directly as solar is generated reduces imports. If you are often out during the day, a battery or shifting suitable appliance use may help you use more of it at home.
Keep bill reduction and export income separate
Avoided import costs reduce your electricity bill. Export payments are a separate income stream. Combining the two can help assess the total benefit, but should not be described as a guaranteed percentage reduction in your bill.
Include the costs that continue
Standing charges usually remain payable. Maintenance, possible equipment replacement, finance costs and changes in tariffs can also affect the long-term result.
A useful quote comparison
- Exact equipment and installation scope.
- Annual generation and self-consumption assumptions.
- Import and export rates used.
- Solar-only and battery options where relevant.
- Warranty details and ongoing support.
- Any grid export limit included in the forecast.
Use our illustrative savings calculator as a starting point, then request a property-specific proposal.
Independent guidance: Energy Saving Trust: solar panel costs and savings.
How can I check a forecast?
Keep the original generation estimate and its assumptions. Ask whether the savings forecast separates direct solar use, battery use and export income, and includes storage losses. An attractive first-year figure does not establish payback if future tariffs, maintenance or replacements are left out.
What if my routine changes?
Working from home, an EV or new heating can change both total demand and its timing. Ask for a comparison based on your current use and a clearly labelled future scenario. Avoid sizing solely around a purchase you have not decided to make.
Reviewed 9 September 2026. General guidance; your installation and any scheme requirements need individual assessment.
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