How Much Electricity Does a Solar Panel Produce in the UK?

A typical 400 to 450 W solar panel facing south at 35 degrees produces about 340 to 470 kWh a year in the UK, by PVGIS figures: about 458 kWh for a 450 W panel in London and 384 kWh in Glasgow. That averages about 0.9 to 1.3 kWh a day, from under 0.3 kWh on a December day in Scotland to nearly 2 kWh on a June day in Cardiff.

A 4 kW system of nine or ten panels therefore produces roughly 3,400 to 4,200 kWh a year, more than Ofgem’s medium household use of 2,500 kWh, but very unevenly across the year. This guide gives the figures by city, month, orientation and tilt, explains what reduces them, and shows how an installer’s MCS estimate compares with the PVGIS model.

Output per panel in nine UK cities

We ran the European Commission’s PVGIS model for nine cities, for panels facing due south at 35 degrees, a typical UK roof pitch, with PVGIS’s standard 14 percent allowance for cable, inverter and other system losses. The figures are long-term averages for 2005 to 2023.

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Three patterns are worth noticing. Latitude matters less than people expect: Aberdeen, at 57 degrees north, produces about as much as Manchester, because long summer days in the north offset the dark winters and Manchester’s climate is cloudy. Local weather matters a great deal: Cardiff and the south coast lead, Glasgow and Manchester trail. And winter output falls much faster in the north: an average December day in Glasgow gives barely half the London figure, while June days are almost the same.

These figures are consistent with our other UK guides: our guide to solar panel installation uses the same PVGIS values for London, Manchester and Edinburgh, and the plug-in solar angle guide uses PVGIS at 30 degrees for 800 W kits.

How to read “kWh per kW”

Solar output scales almost exactly with panel power, so yields are usually quoted per kilowatt of panels, also written kWp (kilowatt peak). Multiply the per-kW figure by your panel capacity in kilowatts to get your yield. A 450 W panel is 0.45 kW; a 4.05 kW array of nine such panels in London gives 4.05 × 1,019 ≈ 4,127 kWh a year.

The rated power is measured under standard test conditions: 1,000 watts of sunlight per square metre and a cell temperature of 25 °C. In Britain, panels reach that intensity only on clear summer middays, and when they do the cells are usually hotter than 25 °C. So a 450 W panel spends most of its working life well below 450 W. Its yearly output is better described by “peak sun hours”: the sunshine on the panel expressed as hours at 1,000 W per square metre. For a London roof at 35 degrees, PVGIS gives about 1,261 kWh of sunshine per square metre a year, or 3.45 peak sun hours a day on average.

PVGIS’s 1,019 kWh per kW in London is about 81 percent of those 1,261 peak sun hours. The 19 percent difference is the combined effect of PVGIS’s 14 percent system loss, heat, reflection off the glass at low sun angles and the spectrum of the light.

Output per square metre of roof

If roof space rather than budget limits you, the useful figure is output per square metre. Current 54-cell roof panels deliver about 210 to 230 W per square metre of panel area, as our guide to solar panel sizes shows from manufacturer data sheets. JinkoSolar’s 450 W Tiger Neo, for example, has a rated efficiency of 22.52 percent.

Multiplying that power density by the yield per kW gives about 215 to 235 kWh per square metre of panel a year in London, 185 to 205 in Manchester and 180 to 195 in Glasgow, facing south at 35 degrees. A typical rear roof slope with room for 20 square metres of panels can therefore produce roughly 3,600 to 4,700 kWh a year, depending on where you live.

A higher wattage on its own does not mean more output per square metre. A 400 W panel and a 450 W panel of the same physical size differ in efficiency; a 400 W panel that is larger simply covers more roof. When you compare quotes with different panels, compare total kW on the roof and the estimated annual kWh, not the number of panels.

Month by month: what a 4 kW system produces

The annual figure hides a large seasonal swing. The table shows a 4 kW system, about nine 450 W panels, at 35 degrees facing south.

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April to August produce about 58 percent of the year’s total in London and about 63 percent in Glasgow. June output is 3.4 times December’s in London, 3.9 times in Manchester and 5.7 times in Glasgow. Over the year the array produces far more than a medium household uses; in December and January it produces less than an average month’s use everywhere in the UK.

PVGIS also reports how much the weather varies between years. For London at 35 degrees the year-to-year standard deviation is about 42 kWh per kW, roughly 4 percent of the average. A sunny year can beat the table by several percent and a dull one fall short by as much; a single month can vary by 10 percent or more.

What a single day looks like

Monthly averages flatten out the weather. To see individual days, we pulled PVGIS’s hourly series for London for 2019 to 2023, for 1 kW of panels at 35 degrees facing south. The average hourly output, in watts per kW of panels, looks like this:

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June hours are shown in British Summer Time, December hours in GMT. Even at the peak of an average June day, 1 kW of panels delivers under half its rated power, because the average mixes clear and cloudy hours. In December the useful window is about six to seven hours, and the midday peak is under a quarter of the panels’ rating.

Individual days spread far wider than the averages. Across the five Junes in the series, a day’s output per kW of panels ranged from 0.76 kWh on the dullest day to 6.73 kWh on the brightest, with a median of about 4.2. One day in ten produced less than about 1.7 kWh, and one in ten more than about 6.3. December ranged from 0.08 kWh to 2.98 kWh per kW, with a median of 0.69. For a single 450 W panel, that means anything from about 0.35 to 3 kWh on a June day, and from almost nothing to about 1.3 kWh on a December day.

Whole years vary less, but still noticeably. In the same series, London’s annual output per kW ranged from 939 kWh in 2021 to 1,089 kWh in 2022, between about 8 percent below and 7 percent above the long-term figure. Judge a new system over a full year, and compare it with the estimate for an average year, not with a sunny neighbour’s best summer.

Comparing output with your electricity use

Ofgem’s typical domestic consumption values, revised from 1 July 2026, set annual use for a single-rate electricity meter at 1,600 kWh (low), 2,500 kWh (medium) and 3,800 kWh (high). Against those:

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Matching annual use on paper is not the same as covering your bills. Output arrives in daylight and mostly in summer; use is spread across evenings and winter. A household out at work typically uses only part of its solar output directly and exports the rest. That is why the sensible size is usually what the roof and budget allow, with exports paid through the Smart Export Guarantee, rather than a precise match to annual consumption. Our guide to solar energy advantages and disadvantages turns these yields into payback figures.

Worked example: a 4 kW system and a medium household in Manchester

This is an example with stated assumptions.

System. Nine 450 W panels, 4.05 kW, on a south-facing roof at 35 degrees. PVGIS: 4.05 × 886 ≈ 3,590 kWh a year.

Household. Medium use of 2,500 kWh a year, assumed for this example to use 40 percent of the solar output directly, about 1,435 kWh.

Result. The household still buys about 1,065 kWh a year from the grid, and exports about 2,155 kWh. At the Ofgem cap unit rate of 26.32p for October to December 2026, the self-used solar is worth about £378 a year; exports earn whatever the export tariff pays.

Seasonal check. In December the array makes about 114 kWh (4.05 × 28.18), against an average month’s use of about 208 kWh, and a December household usually uses more than average. In June it makes about 448 kWh, more than twice the monthly average.

How orientation and tilt change output

Direction matters more than angle. PVGIS figures for London, in kWh per kW of panels a year, with the share of the south-facing 35 degree figure in brackets:

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n/a: not modelled; south-east falls between south and east and behaves like south-west.

The best tilt is forgiving. Anywhere from about 25 to 50 degrees facing south gets within 3 percent of the maximum. PVGIS puts the optimum at 39 to 43 degrees for the nine cities in this guide, a little steeper in the north, but the gain over 35 degrees is under 1 percent everywhere. The Energy Saving Trust gives the same rule of thumb for direction: east or west-facing systems tend to get 15 to 20 percent less than south-facing ones.

Proportions are similar elsewhere. In Manchester, a west-facing roof at 35 degrees gives 702 kWh per kW, 79 percent of the south-facing 886; in Glasgow 683, 80 percent of 853. Vertical south-facing panels lose about a quarter over the year but do relatively well in winter: in a London December they give 43 kWh per kW against 36 at 35 degrees, because the low sun strikes them more squarely.

East-west arrays are common on terraced and semi-detached houses where the ridge runs north-south. They produce about a fifth less than a south-facing array of the same size, but spread their output across the morning and late afternoon, when more of it is used at home.

What else affects output

Temperature

Panels produce less as they warm up. JinkoSolar’s Tiger Neo panel loses 0.29 percent of its power for every degree its cells run above 25 °C. On a sunny summer day cells run well above the air temperature, which costs several percent at that moment. Over a UK year, PVGIS puts the combined loss from heat and low light at about 4.8 percent in London for freely ventilated panels. Panels with no air gap behind them, such as in-roof systems or flexible panels glued down, lose a few percent more.

Shading

Shade is the most common reason a system underperforms. A shadow across one part of a panel can cut its output by far more than the shaded share, because cells are wired in series. Installers following the MCS method assess shade with a sun-path chart: each of 84 segments blocked by a tree, chimney or building cuts the predicted yield by 1 percent. In MCS’s own example, an obstacle more than 10 metres away blocking 11 segments gives a shade factor of 0.89; the same object closer than 10 metres gives 0.6. Microinverters or optimisers reduce the impact of shade on the rest of the array. The MCS method reflects this only in part: where panels feed separate optimisers, inverters or independent MPPT inputs, the installer may calculate a shade factor for each sub-array instead of one for the whole roof.

Degradation

Panels slowly lose output. JinkoSolar’s warranty for its Tiger Neo 54-cell panel allows about 1 percent loss in the first year, then about 0.4 percent a year, ending at 87.4 percent of rated power after 30 years. On that curve a panel delivers about 95 percent of its original output in year 10 and 89 percent in year 25. Check the warranty curve of the panel you are offered; it states the guaranteed output for each year.

Dirt, snow and system faults

Rain keeps tilted panels in most of the UK reasonably clean; flat or shallow panels near trees, farms or coasts collect more grime. Snow stops output until it slides off. The most expensive losses are usually undetected faults: a tripped isolator or a failed inverter can cost weeks of output. Our guide to solar panel cleaning and servicing explains what is worth checking.

Inverter size

Many UK systems pair 4 to 4.5 kW of panels with a 3.68 kW inverter, so the installation stays within the G98 limit of 16 A per phase and can be notified after commissioning. On the few hours a year when the panels could deliver more than 3.68 kW, the inverter caps the output. Because UK panels so rarely reach full rated power, the loss is usually small. In PVGIS’s hourly series for London from 2019 to 2023, the hourly output of a south-facing array at 35 degrees never exceeded 882 W per kW of panels, so a 4.05 kW array on a 3.68 kW inverter, a ratio of 0.91, would not have been capped in any hour. Short bright spells inside an hour can exceed that, so ask the installer to state any expected clipping in the estimate.

The MCS estimate versus PVGIS

An MCS-certified installer must give you a written performance estimate before you sign. It uses a simple formula agreed by the MCS working group and described by the Building Research Establishment:

Annual output (kWh) = kWp × Kk × SF

• kWp is the panel capacity.
• Kk is the annual yield per kW for your location, orientation and pitch, taken from tables based on SAP climate regions. The BRE document notes that Kk already includes an assumed performance ratio of 0.8.
• SF is the shade factor from the sun-path method above, 1 for no shade.

PVGIS works differently: it models each hour from satellite sunshine data for your exact coordinates and the horizon around them, then applies temperature, reflection and system losses. Its effective performance ratio for a London roof, about 0.81, is close to the MCS assumption of 0.8, so for an unshaded south-facing roof the two methods usually land in the same range. Differences come from the climate data periods, regional averaging in the MCS tables and the shade assessment.

Use them together. If an installer’s figure is far above PVGIS for your postcode and orientation, ask why. If it is far below, ask how shade was assessed. MCS says its shade method should be within 10 percent of the actual annual yield for most systems, which is about the size of a good or bad weather year.

Estimating your own panel output step by step

Differences between England, Scotland, Wales and Northern Ireland

England

In our data English yields range from 886 kWh per kW in Manchester to 1,019 in London, with Birmingham at 968 and Newcastle at 949. The south-west does better still: our plug-in angle guide gives about 891 kWh for 800 W at 30 degrees in Plymouth, roughly 1,110 kWh per kW, and PVGIS gives about 1,120 kWh per kW there at 35 degrees.

Scotland

The central belt is the least productive part of Great Britain in our data, at 853 kWh per kW in Glasgow and 903 in Edinburgh, but the east coast does better than its latitude suggests: Aberdeen reaches 893. December output is the lowest in the UK, which matters for anyone hoping to cover winter use.

Wales

Cardiff gives the highest annual figure of our nine cities, 1,042 kWh per kW, helped by its southern position. Upland and west-coast sites are cloudier; check PVGIS for your own location rather than assuming the Cardiff figure.

Northern Ireland

Belfast produces about 919 kWh per kW, a little above Edinburgh and Manchester. The physics are the same, but the money is not: the Smart Export Guarantee does not apply in Northern Ireland, so exported electricity earns only what local suppliers choose to pay. That makes self-use, and therefore system size, more important to the payback.

What a plug-in kit produces in comparison

A plug-in solar kit is limited to 800 W of output in Great Britain. PVGIS gives about 808 kWh a year for 800 W of panels at 30 degrees facing south in London, and about 676 kWh in Glasgow. The government’s July 2026 impact assessment, using average UK sunshine, models 690 kWh at 30 degrees facing south and 378 kWh for panels hung vertically facing east or west. A typical kit therefore produces about a fifth of a 4 kW rooftop system. Our guide to what plug-in solar saves in the UK shows what that output is worth.

Common mistakes when estimating output

• Multiplying rated watts by daylight hours. A 450 W panel does not produce 450 W for 12 hours. Fix: use kWh per kW from PVGIS or the MCS tables.
• Using an annual average for winter. The average day is 1.26 kWh per 450 W panel in London, but a December day is 0.53. Fix: look at the monthly figures.
• Ignoring near shade. A chimney or dormer within 10 metres can cut output by far more than its size suggests. Fix: assess shade at different times of year or ask for an MCS shade factor.
• Comparing estimates with different losses. One calculator’s 1,100 kWh per kW and another’s 950 may differ only in assumed losses. Fix: check the system loss setting.
• Expecting year-one output for 25 years. Fix: allow about 0.4 percent loss a year on current panels.
• Assuming the north is hopeless. Aberdeen produces as much as Manchester. Fix: model your own location.

Next steps

• Solar installation in the UK: process, timeline and cost
• Solar panel sizes and how many fit on a UK roof
• Solar energy advantages and disadvantages in UK numbers