UK peak sun hours per day by month: the table below uses official PVGIS horizontal-plane irradiation at five city coordinates. These are 2020–2023 monthly averages, not forecasts or measured campervan output.
| Month | London | Manchester | Cardiff | Edinburgh | Inverness |
|---|---|---|---|---|---|
| January | 0.82 | 0.59 | 0.77 | 0.52 | 0.37 |
| February | 1.49 | 1.17 | 1.45 | 1.17 | 0.97 |
| March | 2.62 | 2.45 | 2.71 | 2.40 | 2.24 |
| April | 4.44 | 4.16 | 4.55 | 3.94 | 3.70 |
| May | 5.15 | 4.64 | 5.64 | 4.56 | 4.29 |
| June | 5.52 | 5.11 | 5.73 | 5.00 | 4.92 |
| July | 5.11 | 4.33 | 5.22 | 4.69 | 4.35 |
| August | 4.31 | 3.91 | 4.37 | 3.82 | 3.64 |
| September | 3.25 | 2.89 | 3.20 | 2.62 | 2.46 |
| October | 1.85 | 1.47 | 1.79 | 1.32 | 1.17 |
| November | 1.02 | 0.76 | 0.99 | 0.69 | 0.54 |
| December | 0.60 | 0.48 | 0.55 | 0.34 | 0.26 |
Download the table as CSV or inspect the original API responses.
What peak sun hours mean
Peak sun hours express daily solar irradiation as equivalent hours at 1kW per square metre. They are not daylight hours. A long grey day can have much less available solar energy than a shorter clear one.
Our calculation and its limits
Source: European Commission Joint Research Centre, PVGIS monthly radiation service, retrieved 21 September 2026. The returned radiation database is PVGIS-SARAH3. We requested horizontal irradiation for 2020–2023, divided each monthly total by that month's actual day count, then averaged the four daily values for each calendar month. February includes the 2020 leap day. Values are rounded only for display.
The five coordinates are London (51.5074, −0.1278), Manchester (53.4808, −2.2426), Cardiff (51.4816, −3.1791), Edinburgh (55.9533, −3.1883) and Inverness (57.4778, −4.2247). They are reference points, not measurements for entire regions. Four years is a limited planning sample rather than a long-term climate normal. Terrain horizon treatment comes from PVGIS; local trees, roof equipment and buildings are not represented.
Turn PSH into an energy estimate
Use panel watts × peak sun hours × assumed system factor = daily Wh. For a transparent example, 400W × 4 PSH × 0.8 gives 1,280Wh/day. The 0.8 factor is an illustrative allowance, not a measured efficiency for your van. At 0.7 PSH the same assumptions give only 224Wh/day.
If your loads use 900Wh/day, that winter example leaves a 676Wh daily shortfall. More battery capacity can bridge a limited gap, but it cannot generate the missing energy. Plan alternator or hook-up charging, reduce demand, or change the itinerary. Model several poor days together rather than treating a monthly average as a daily minimum.
Flat roof panels versus tilted panels
These values describe a horizontal surface, making the reference plane useful for a near-flat campervan roof. A tilted portable panel needs an appropriate plane calculation. Temperature, dirt, shade, controller behaviour and battery acceptance all affect output; the table alone cannot predict a particular system's production.
Questions about UK solar planning
Which city should I use?
Choose a nearby reference for a first estimate, then obtain PVGIS data for the actual travel area and panel orientation. Use the months you will travel rather than an annual average.
Are peak sun hours the same as sunshine hours?
No. PSH is an energy-equivalent measure at a defined irradiance, while sunshine or daylight duration measures time.
Will a 400W panel produce 400W whenever it is sunny?
No. Nameplate output is specified under test conditions. The sun angle, temperature, shading and system limits change actual power.
Can I rely on the monthly figure every day?
No. Weather varies within each month. Keep a reserve and a second charging source for essential loads.
Use the solar setup guide, compare 200W and 400W arrays, check winter solar planning, and enter your appliances in the free electrical planner.
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Jack Kennedy is a self-builder who has built two vans. He created Roam Wired to simplify conversion planning and share free tools, supported by affiliate links.
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