Solar panels
Solar output through the year
UK solar panels generate most from April to September and very little in December and January. The calculator below shows the monthly pattern for your postcode and roof.
Updated 3 October 2026 · energy.org.uk editorial team
The pattern through the year
Generation follows daylight hours and the height of the sun. In the UK, the summer months can each produce several times as much as a winter month. Most of a system's yearly output comes between spring and early autumn.
This matters because household electricity use is usually highest in winter, so panels cover much less of your use then. If you plan to add a heat pump, nearly all of its extra use will be in the months when panels generate least.
Calculator
Monthly solar generation for your postcode
Working out sunlight for this location…
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How this estimate works
Your location sets how much sunlight the panels get. We use long-term average sunlight for your area from PVGIS 5.3, European Commission Joint Research Centre.
Roof direction matters: south-facing roofs generate most, east and west a little less, north the least. If you are not sure, we assume east/west rather than the best case.
A bigger system generates more. Without a size, we use a typical system for the roof size you chose.
Shading from trees, chimneys or nearby buildings reduces output. Allowance is also made for normal wiring and inverter losses.
The electricity value assumes a typical home that is in some of the day, saving the current Ofgem price-cap unit rate, with the rest paid at Octopus Energy Outgoing Smart Export Guarantee (12-month fixed) export rate. These are estimates, not guarantees; an installer's survey will be more precise.
Method version 1.0, checked 2026-10-01. PVGIS · Ofgem typical use
Why your output differs from the estimate
- Weather. The estimates use long-term average sunshine. A dull summer or a sunny spring can move a month's output well above or below the average.
- Shade from trees in leaf, or a low winter sun behind buildings.
- Faults, such as an inverter that has tripped. A sudden drop on a sunny day is worth investigating.
Check
What to check first
- Compare like with like: the same month in different years, or a month against its estimate, rather than one week.
- Your monitoring app or inverter display, for the system's total generation.
- The installer's performance estimate, from your handover documents.
Do
Practical next steps
- Note your system's generation each month.
- Compare it with the monthly estimate for your postcode in the solar panel calculator.
- Use more electricity in the middle of the day in summer, such as timed laundry or EV charging.
- If output is consistently well below the estimate, see solar maintenance and poor output.
Take care
Important limitations
- Monthly estimates are long-term averages from PVGIS, not a forecast for this year.
- The estimates allow for typical system losses, but not for specific faults or new shade.
Related tools and guides
Sources
Official sources checked 3 October 2026.