Do solar panels work in winter on the Isle of Man?
The short answer
Yes, all year round. December makes about a sixth of what May does.
On a south-facing Douglas roof, each kWp of panels makes about 23 kWh in December and about 142 kWh in May. November to January together gives about 8% of the year’s electricity. A south-facing wall does better than a roof in midwinter, because the winter sun is low.
The island’s winter days are short and the sun stays low, so panels make far less from November to January than in summer. They still work every day there is daylight. This guide shows the island’s month-by-month figures, which way to face panels for winter, and what it means for a plug-in kit or a rooftop system.
Month by month
| Month | kWh per kWp | A 4 kWp roof system | Share of the year |
|---|---|---|---|
| January | 30 | 120 kWh | 3% |
| February | 51 | 202 kWh | 5% |
| March | 88 | 352 kWh | 9% |
| April | 124 | 495 kWh | 12% |
| May | 142 | 569 kWh | 14% |
| June | 137 | 549 kWh | 13% |
| July | 133 | 532 kWh | 13% |
| August | 120 | 479 kWh | 12% |
| September | 92 | 369 kWh | 9% |
| October | 60 | 239 kWh | 6% |
| November | 35 | 138 kWh | 3% |
| December | 23 | 91 kWh | 2% |
May to July together gives about 40% of the year’s electricity. A 4 kWp roof system in Douglas makes about 91 kWh in December and about 549 kWh in June.
Which way to face panels for winter
| Where and how | December | November to January | Whole year |
|---|---|---|---|
| Douglas, south, 35 degrees | 23 | 87 | 1034 |
| Port Erin, south, 35 degrees | 23 | 86 | 1043 |
| Ramsey, south, 35 degrees | 23 | 86 | 1003 |
| Peel, south, 35 degrees | 22 | 81 | 999 |
| Douglas, south, 20 degrees | 18 | 69 | 989 |
| Douglas, flat | 9 | 38 | 853 |
| Douglas, west, 35 degrees | 9 | 38 | 825 |
| Douglas, east, 35 degrees | 9 | 40 | 785 |
| Douglas, south-facing wall | 27 | 101 | 750 |
Three things stand out:
- The whole island is much the same in winter. Douglas, Port Erin, Ramsey and Peel all make between 22 and 23 kWh per kWp in December.
- Steeper is better in winter. A south-facing wall makes about 27 kWh per kWp in December, more than a roof at 35 degrees, and about 101 from November to January. Over the whole year the wall makes less, because it misses the high summer sun.
- Flat, east and west lose most. Each makes about 9 kWh per kWp in December, under half a south-facing roof.
Modelled with the European Commission’s PVGIS 5.3, using satellite records of the island’s weather from 2005 to 2023 and allowing 14% for system losses, queried on 30 September 2026. Cloudy days are already in the figures. Real output also depends on shading, dirt and the age of the panels.
What it means for a plug-in kit
A plug-in kit follows the same pattern on a smaller scale. A kit on a south-facing wall or balcony rail suits winter well, because steep panels catch the low sun. Our savings calculator shows a two-panel kit’s output month by month, tilted or on a wall, and works out what it saves at Manx Utilities’ 29.5p a unit.
What it means for a rooftop system
Winter output is small, but every unit you use at home is worth 29.5p, against 9.7p for a unit exported under the Sustainable Generation tariff. Summer is where most of a system’s yearly value comes from, so judge a system on the whole year. Our quote checker does that for your roof, and a home battery can carry spare daytime power into the evening.
If you are thinking about a heat pump, it works hardest in winter, when panels make least, so most of its winter electricity will come from the grid. Our heat pump guide covers the island grant and Manx Utilities’ tariff for electric heating.
Related guides
- Solar panels on the Isle of Man
- What solar panels cost, and how to check a quote
- Plug-in solar savings calculator
- Home batteries and solar
Common questions
Do solar panels work in winter on the Isle of Man?
Yes. On a south-facing Douglas roof, each kWp of panels makes about 23 kWh in December and about 30 kWh in January, against about 142 kWh in May. November to January together gives about 8% of the year’s output.
How much does a 4 kWp system make in December?
About 91 kWh on a south-facing Douglas roof at 35 degrees, against about 549 kWh in June, using PVGIS figures for the island.
Which way should panels face for the most winter power?
South, and steep. A south-facing wall makes about 27 kWh per kWp in December, more than a south-facing roof at 35 degrees. Flat, east and west-facing panels make about 9.
Do solar panels work on cloudy days?
Yes, at a lower rate. The figures on this page come from satellite records of the island’s real weather from 2005 to 2023, so cloudy days are already counted in them.