How to estimate your own solar savings in Scotland
You can estimate solar savings with four inputs: how much electricity you use a year, your day and night unit rates, how much your roof could generate, and how much of that you would use at home. Work out the units you would stop buying and value them at your day rate, then add the battery and export effects.
Last updated: 5 November 2026.
Reviewed by the Scottish Energy Efficiency team.
What do you need before you start?
Gather a recent electricity bill or annual statement. You need your yearly usage in kWh, your day unit rate, any night rate if you are on a time-of-use tariff, and your standing charge. Standing charges do not change with solar, so leave them out of the savings sum.
Your annual statement usually shows an estimated or actual yearly consumption figure. If you only have monthly bills, add up twelve months of kWh rather than multiplying one month, because Scottish usage swings a lot between summer and winter.
Note how your household uses power across the day. A home that is busy during daylight hours uses more solar directly than one that is empty from eight until six. That single habit changes the result more than most people expect.
- Annual electricity use in kWh
- Day unit rate (pence per kWh)
- Night or off-peak rate, if you have one
- Roof direction, pitch and any shading from trees or neighbouring buildings
- Whether you are at home during the day
How much will the panels generate?
Generation depends on system size, roof direction, pitch, shading and location. A proper quotation uses the MCS method, which applies a postcode-based sunshine zone, your roof direction and pitch, and a shading factor. That is far more reliable than a national average, and it is worth asking any installer to show the figures they used.
East or west roofs produce less than a south-facing roof but spread generation across the day, which can suit households that use power in the morning and evening.
Generation is heavily seasonal. Long Scottish summer days produce most of the annual total, while December and January contribute relatively little. Plan your expectations around the year, not around a single sunny week.
How do you turn generation into a saving?
Split generation into units used at home and units exported. Units used at home are worth your day rate, because they displace electricity you would otherwise buy. Exported units are worth whatever your supplier pays under the Smart Export Guarantee, which is usually much less. Add the two, and the battery effect if you have one.
This is the step most online calculators blur. A unit you use yourself displaces a unit you would otherwise buy, so it is worth the full day rate. A unit you export is worth whatever your supplier pays, which is usually much less.
If you are unsure what share you would use at home, try two or three scenarios rather than one optimistic guess. It is far better to know the range than to rely on a single headline number.
| Step | What you calculate |
|---|---|
| 1 | Annual generation, from the MCS estimate for your roof |
| 2 | Share used at home, based on your daytime usage pattern |
| 3 | Units used at home valued at your day rate |
| 4 | Exported units valued at your SEG rate |
Where do estimates usually go wrong?
Estimates usually go wrong by assuming you use almost all the generation yourself, by valuing exported units at the day rate, or by building in steep energy price rises. Each makes the number look better on paper without changing what actually happens to your bill.
Price growth is an assumption, not a fact. Energy prices can rise or fall, so treat any calculation that relies on future increases with caution and ask to see the figure without them.
For how a battery changes the sum, read our solar battery savings guide. For how export rates compare, see the Smart Export Guarantee guide. Both plug straight into the steps above.
Frequently asked questions
Is an online solar calculator accurate for Scotland?
Only as accurate as its inputs. Many calculators use UK-wide averages and assume high self-use. Use your own annual kWh, your own unit rates and a realistic share used at home for a fairer estimate.
Should I include my standing charge in the savings?
No. You still pay the standing charge with solar panels, so it does not form part of the saving. Only the units you stop buying count.
How do I find my annual electricity use?
Check your annual statement or your supplier app. If neither shows a yearly total, add up twelve months of bills to capture both summer and winter usage.
More solar savings guides
How do you get a solar savings quote?
Fill in the form and we will model the arithmetic and send a written quotation from our MCS-certified partner.