What the Met Office record says about Manchester
Manchester is wetter than southern England, but not as dull as its reputation. The Met Office publishes no long-term averages for a Manchester Airport station. The nearest fair reference is Woodford, in Stockport borough, about 17 km from Manchester Town Hall (Met Office long-term averages).
Across 1991 to 2020, Woodford logged 1,385 sunshine hours in an average year. Its yearly rainfall averaged 868 mm, and a millimetre or more fell on 156 days in a typical year. That is a lot of wet days. It still leaves most days of the year dry.
Rain is not spread evenly across the city-region. Rochdale, up against the Pennines, is the wetter and duller contrast, and the gap is large:
| Measure | Woodford (Stockport borough) | Rochdale |
|---|---|---|
| Sunshine | 1,385 hours | 1,265 hours |
| Rainfall | 868 mm | 1,197 mm |
| Days with 1 mm of rain or more | 156 | about 171 |
A roof in the city itself sits at the drier, sunnier end of Greater Manchester. Within the city, local shade from trees, chimney stacks and taller buildings will usually matter more to one roof than which weather station happens to be nearest.
Panels need daylight, not heat
Solar panels turn light into electricity. They do not need warm weather or a cloudless sky. Under thin, bright cloud they keep working at a reduced rate. Under thick grey cloud the output falls further, but daylight still produces some power.
Heat works slightly against them. Panels lose a little efficiency as they get hotter, so a cool, clear spring day can be a very good day for a Manchester roof. PVGIS gives April almost the same output as July on the best roof: 105 against 106 kWh per kW. The strong months are strong because the days are long and the sun is high, not because they are warm.
None of the figures on this page assume good weather. PVGIS, the European Commission's solar model, works out what a 1 kW system would make from satellite records of the real sky over Manchester for 2005-2023. It uses the PVGIS-SARAH3 data set and allows 14% for system losses such as wiring and the inverter (PVGIS). The drizzle, the grey Februaries and the short December days are all inside the result.
Month by month on the best Manchester roof
Summer carries the year. The table shows PVGIS output for each month on the best-placed roof in central Manchester, which faces just east of due south at a 39° tilt.
| Month | kWh per kW | Share of the year |
|---|---|---|
| January | 28 | 3% |
| February | 46 | 5% |
| March | 79 | 9% |
| April | 105 | 12% |
| May | 112 | 13% |
| June | 109 | 12% |
| July | 106 | 12% |
| August | 96 | 11% |
| September | 81 | 9% |
| October | 58 | 7% |
| November | 39 | 4% |
| December | 30 | 3% |
Monthly figures from PVGIS 5.3 are rounded, so they add to 889 rather than the yearly 888. Shares are our arithmetic.
Three things stand out. May is the strongest month at 112 kWh per kW, about 3.7 times December's 30, by our arithmetic. April to September together give 69% of the year's output (PVGIS, our arithmetic). And January is the weakest month of all, at 28.
For a household, that means panels can cover a good part of daytime use from spring to early autumn, and only a small part in midwinter. Take the Energy Saving Trust's typical home system of 4.5 kWp (Energy Saving Trust). On this roof it would make about 4,000 kWh a year by our arithmetic, against typical household use of 2,500 kWh as Ofgem measures it (Ofgem). Most of that output arrives between April and September.
These are long-run averages, and single years vary. A dull summer will come in below them and a bright one above. Plan around the average, and judge a system over several years rather than one wet August.
Five weather myths, checked against the data
"It's too cloudy here for solar"
The cloud is already counted. The 888 kWh per kW figure comes from satellite records of Manchester's own sky, overcast days included. It is a measured result for this city, not a sunny-day estimate that the local weather will spoil.
"Panels need hot sunshine"
They need light. Warmth slightly lowers their efficiency, and the long days of late spring do more than summer heat. PVGIS puts May, with its long days, slightly ahead of July.
"Rain will damage them"
Panels are built to sit outside for decades; the Energy Saving Trust expects them to last 25 years or more. Rain does them no harm. It rinses dust and pollen off the glass, which helps on a steep slate roof that nobody wants to climb.
"They make nothing in winter"
They make little, not nothing. December still gives 30 kWh per kW on the best roof. Snow that settles stops output until it slides or melts off, though the short days are the bigger limit.
"Only a south-facing roof is worth it"
South is best, but it is not the only option. At a 35° pitch an east roof makes 717 kWh per kW and a west roof 702, while panels laid flat make 745. The guide to east and west roofs compares every direction.
What decides it for your home
With the weather set aside, five things about the household decide whether solar suits it. Rain is not one of them.
- Daytime use. Panels produce most from late morning to mid-afternoon. A home where someone works from home, or where the washing machine and dishwasher run in daylight, uses more of its own output directly. A home that is empty until evening sends more to the grid; the export guide explains how that is paid for.
- The roof. Direction and pitch set the output, and the roof's condition sets the timing. Panels last 25 years or more, and an inverter typically needs replacing after around 12 years. A roof that will need work within a few years is best repaired first. Older slate roofs have their own guide to older homes.
- Shade. A chimney stack, a tall tree or a taller building next door can cost a roof more output than the weather does. Ask an installer to assess shade across the whole year, when the sun is low as well as high.
- How long you will stay. Panels stay with the house. If a move is likely soon, they become part of what you sell rather than something you use for long.
- Whose roof it is. 61.8% of Manchester households rent (ONS Census 2021), and a tenant cannot add panels alone. The renting guide covers what tenants can do.
A fair test before you commit
You can check any quote against the weather data yourself. A quote from an MCS-certified installer should include an estimate of the system's yearly output in kWh. Divide that figure by the kW size of the system, then set the answer beside the PVGIS figure for your roof's direction and pitch.
- If the two are close, the estimate is grounded in Manchester's real weather.
- If the quote is far higher, ask how it was worked out and what shading was allowed for.
- If it is far lower, ask what the installer saw on the roof that the model cannot know about, such as a tree or a stack.
Then set the yearly kWh against what your household uses, which is on your bills, and think about how much of it falls in daylight. That comparison, in kWh, says more about whether solar suits you than any forecast for the summer.
To test your own roof, the roof yield explorer uses the same PVGIS data for every direction and pitch. For prices, the cost guide sets out what North West homes actually paid for MCS-certified systems.
The city has its own reason to care. Manchester City Council puts the solar Manchester will need by 2030 at almost 400 megawatts, as one step towards zero carbon by 2038 (Manchester City Council). That plan was written for this climate, with this rain.