How much electricity solar panels actually produce
A kilowatt of panels on a south-facing UK roof makes roughly the same amount every year, and the two things that change it are which way the roof faces and where in the country it is. Both are measurable, and both are below.
4 kWp, facing south
kWh a month- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
3,967 kWh a year, and 69% of it falls between April and September.
A 4 kWp array, facing south
3,967 kWh
A year, averaged over every council PVGIS models
Per kilowatt installed
992 kWh
The figure every other number on this page is built from
Facing east or west instead
79%
Of what the same panels make facing south
Sunniest council to dullest
59%
Lewes against Shetland Islands
PVGIS (European Commission Joint Research Centre), modelled from 2005 to 2023 weather at a 35° pitch with 14% system losses, for the centre of each of 361 councils. Modelled output, not metered generation.
By size
Output by system size and roof direction
A panel is around 0.4 kWp, so a 4 kWp array is about ten of them and takes roughly 20 square metres of roof. Pick your size down the side and your roof direction across the top.
| Array size | South | South-east | South-west | East | West |
|---|---|---|---|---|---|
| 2 kWp | 1,984 | 1,871 | 1,861 | 1,575 | 1,560 |
| 3 kWp | 2,976 | 2,806 | 2,791 | 2,362 | 2,340 |
| 4 kWp | 3,967 | 3,742 | 3,722 | 3,150 | 3,121 |
| 5 kWp | 4,959 | 4,677 | 4,652 | 3,937 | 3,901 |
| 6 kWp | 5,951 | 5,613 | 5,583 | 4,725 | 4,681 |
kWh a year, averaged over every council. A 35° pitch and no shading: a dormer, a chimney or a neighbour's conifer takes more off the total than the difference between two of these columns.
A day, averaged over the year
10.9 kWh
What a 4 kWp array makes on an average day. Useful for arithmetic, and true of almost no actual day.
A day in June
16.2 kWh
The month that carries the year. This is the day people remember when they judge the system.
A day in December
4.0 kWh
June makes about 4.0 times as much, which is why a battery does less in winter than the brochure implies.
By month
69% of the year's generation lands in six months
Solar in the UK is a summer crop. That is not an argument against it — it is an argument for knowing what your winter bill will still look like, and for not sizing a battery against a June afternoon.
A 4 kWp south-facing array, month by month
kWh generated, averaged over every council PVGIS models.
Peak: May 494
June makes about 3.9 times what December does. Panels work in the cold; they do not work in the dark.
Every roof direction, season by season
kWh from a 4 kWp array. East and west are flatter across the year than south is.
| Direction | Win | Spr | Sum | Aut |
|---|---|---|---|---|
| South | 470 | 1,292 | 1,413 | 793 |
| South-east | 394 | 1,240 | 1,398 | 711 |
| South-west | 393 | 1,229 | 1,391 | 709 |
| East | 237 | 1,080 | 1,301 | 532 |
| West | 235 | 1,064 | 1,294 | 527 |
A flatter curve is worth more than it looks: an east-west split roof generates through more of the day, which is when most households actually use electricity.
By direction
East and west lose less than people expect
The received wisdom is that anything other than south is not worth doing. The modelled figures disagree: a west-facing roof gives up less than a fifth, and gives it up at times of day when electricity is worth less anyway.
A 4 kWp array by roof direction
kWh a year, averaged over every council.
- South100% of south3,967 kWh
- South-east94% of south3,742 kWh
- South-west94% of south3,722 kWh
- East79% of south3,150 kWh
- West79% of south3,121 kWh
North-facing roofs are not modelled here. They generate, but rarely enough to justify the scaffolding.
Two slopes beat one
Splitting an array across an east and a west slope generates less in total than putting it all on the south one, but spreads it across the morning and the evening. If you are at home in the day, or you have a battery to fill, that shape is often worth more than the extra kilowatt hours.
What the model leaves out
Shading, which is the single largest thing that goes wrong on a real roof. PVGIS models a clear horizon at the council's centre point. A survey that puts a scanner on your actual roof is the only thing that answers the shading question.
By place
Where you are matters less than which way the roof faces
The gap between the sunniest part of the country and the dullest is real, and it is smaller than the gap between a south-facing slope and an east-facing one. Both are smaller than the gap between a shaded roof and a clear one.
A 4 kWp south-facing array by region
kWh a year, each council inside the region counting once.
- South East4,282
- East of England4,199
- South West4,146
- London4,113
- East Midlands3,976
- West Midlands3,901
- Wales3,871
- Yorkshire and The Humber3,854
- North East3,802
- North West3,641
- Northern Ireland3,583
- Scotland3,434
PVGIS models the centre point of every council, so a large region averages over a lot of ground.
Hours of sunshine a year
Met Office HadUK-Grid long-term averages, by council, averaged over each region.
- South East1,685
- East of England1,633
- South West1,605
- London1,598
- East Midlands1,519
- West Midlands1,493
- North East1,488
- Wales1,463
- Yorkshire and The Humber1,458
- North West1,402
- Northern Ireland1,290
- Scotland1,288
Sunshine hours and modelled generation rank almost the same way, which is the sanity check on both.
Method
What these numbers are, and what they are not
Every figure on this page is modelled. Nobody publishes metered generation for domestic roofs by council, so anyone who claims to know what your roof made last year is guessing more confidently than we are.
- Source
- PVGIS, the European Commission's Joint Research Centre photovoltaic tool, as published on 31 December 2023.
- Weather
- 2005 to 2023, so a long enough run that one poor summer doesn't move it.
- Assumptions
- Crystalline silicon panels at a 35° pitch, 14% system losses, a clear horizon and no shading.
- Geography
- One model run at the centre point of each of 361 local authorities.
- Sunshine
- Met Office HadUK-Grid long-term monthly averages, to 31 December 2020, assigned to councils by grid cell.
- Not included
- Shading, panel degradation, inverter clipping, snow, and whatever the installer actually fits.
Questions
Common questions about solar output
How much does a 4kW solar system produce per day in the UK?
About 10.9 kWh averaged across the year, on a south-facing roof at a 35° pitch. That average hides the shape of it: a June day makes several times a December one, so the daily figure is useful for annual arithmetic and useless for planning a winter evening.
How much electricity do solar panels produce in the UK in a year?
Around 992 kWh per kilowatt installed, facing south, averaged over every council. A 4 kWp array — roughly ten panels — comes to about 3,968 kWh a year. Modelled, not metered.
Do east-west facing solar panels work?
Yes. An east or west slope models at about 79% of the south-facing figure, and generates across more of the day. For a household that is in during daylight, or has a battery, the flatter curve often earns more than the extra kilowatt hours a south roof would have made.
Does it matter where in the UK I live?
Less than most people assume. The best council PVGIS models generates about 59% more than the worst. Roof direction moves the answer by more than that, and shading moves it by more again.
Is this what my roof will actually make?
No, and nothing that gives you a number without looking at your roof can tell you that. This is a model of a clear roof at a standard pitch in your area. Shading, the pitch you actually have, the inverter that gets fitted and the panel spec all move it. Treat it as the number to sanity-check a quote against.
Do panels stop working in winter?
They work in the cold — better than in extreme heat, in fact. What they need is light, and a UK December has about a fifth of the useful daylight of a June. That is why the monthly chart on this page matters more than the annual total when you are sizing a battery.
Output is half the question. What it is worth depends on what you use at home and what your supplier pays for the rest: the payback page prices these figures at the published cap rate and a real export tariff, and the solar guide covers whether the roof suits panels at all.
What would your roof make?
Enter a postcode and we'll use the modelled generation for that council, and the export rates on offer there.