How Much Electricity Does a Commercial Solar Panel Produce?
Updated 23 October 2026 · SEO Dons Editorial
How much electricity does one panel make in a year?
A 550 W commercial panel on a south-facing 35 degree roof makes about 469 kWh a year in Glasgow and 617 kWh in Plymouth, according to PVGIS. On low-tilt east-west rows the same panel makes about 389 to 512 kWh. The table scales PVGIS results for 1 kWp by panel wattage, which holds because PVGIS output is proportional to capacity.
| Location | Layout | kWh per kWp a year | 450 W panel, kWh a year | 550 W panel, kWh a year | 600 W panel, kWh a year |
|---|---|---|---|---|---|
| Plymouth | South, 35° | 1,122 | 505 | 617 | 673 |
| Plymouth | East-west, 10° | 932 | 419 | 512 | 559 |
| Birmingham | South, 35° | 968 | 436 | 532 | 581 |
| Birmingham | East-west, 10° | 800 | 360 | 440 | 480 |
| Manchester | South, 35° | 886 | 399 | 487 | 532 |
| Manchester | East-west, 10° | 741 | 333 | 407 | 444 |
| Glasgow | South, 35° | 853 | 384 | 469 | 512 |
| Glasgow | East-west, 10° | 707 | 318 | 389 | 424 |
Two things stand out. Location moves the figure more than panel brand does: the same south-facing panel makes about 32% more in Plymouth than in Glasgow. And layout costs about 16% to 17% where a flat roof carries east-west rows instead of a tilted south-facing rack. The east-west figure is the average of an east-facing and a west-facing plane, each at 10 degrees. Units are explained on the kWp, kW and kWh page.
How many kWh a day does a panel make, month by month?
These tables give the average kWh per day from one 550 W panel in each month, from the same PVGIS runs. Multiply by the days in the month for a monthly total, and by 0.82 for a 450 W panel or 1.09 for a 600 W panel.
South-facing, 35 degree tilt
| Month | Plymouth | Birmingham | Manchester | Glasgow |
|---|---|---|---|---|
| Jan | 0.73 | 0.66 | 0.48 | 0.42 |
| Feb | 1.17 | 1.01 | 0.87 | 0.79 |
| Mar | 1.69 | 1.49 | 1.39 | 1.28 |
| Apr | 2.37 | 1.99 | 1.92 | 1.89 |
| May | 2.45 | 2.08 | 2.01 | 2.06 |
| Jun | 2.53 | 2.15 | 2.03 | 2.02 |
| Jul | 2.40 | 2.10 | 1.92 | 1.97 |
| Aug | 2.23 | 1.88 | 1.72 | 1.72 |
| Sep | 1.90 | 1.65 | 1.49 | 1.38 |
| Oct | 1.25 | 1.12 | 1.00 | 0.93 |
| Nov | 0.90 | 0.78 | 0.69 | 0.61 |
| Dec | 0.64 | 0.59 | 0.50 | 0.34 |
East-west, 10 degree tilt
| Month | Plymouth | Birmingham | Manchester | Glasgow |
|---|---|---|---|---|
| Jan | 0.35 | 0.29 | 0.22 | 0.17 |
| Feb | 0.70 | 0.59 | 0.51 | 0.44 |
| Mar | 1.26 | 1.11 | 1.03 | 0.94 |
| Apr | 2.04 | 1.73 | 1.67 | 1.62 |
| May | 2.38 | 2.03 | 1.96 | 1.97 |
| Jun | 2.56 | 2.18 | 2.06 | 2.02 |
| Jul | 2.40 | 2.09 | 1.92 | 1.95 |
| Aug | 2.04 | 1.75 | 1.61 | 1.58 |
| Sep | 1.51 | 1.32 | 1.20 | 1.09 |
| Oct | 0.84 | 0.73 | 0.66 | 0.58 |
| Nov | 0.46 | 0.37 | 0.32 | 0.26 |
| Dec | 0.28 | 0.23 | 0.19 | 0.12 |
A south-facing 35 degree panel in Glasgow averages 1.28 kWh a day over the year, but only 0.34 in December and 2.02 in June. Low-tilt east-west rows hold up well in summer (in June they match or beat the tilted south figure in all four cities) and fall away in winter, when they make 34% to 44% of what the tilted panel makes in December. The reasons for the seasonal swing are on the monthly output page.
What moves the output of a single panel?
- Location. Latitude and weather set the baseline, as the 1,122 against 853 kWh per kWp gap between Plymouth and Glasgow shows.
- Tilt and orientation. PVGIS measures azimuth from due south, where "90° is East, 0° is South and 90° is West". Dropping a south-facing panel from 35 to 10 degrees gives 90% to 91% of the 35 degree output in these four cities, in return for a lower profile on a flat roof.
- Temperature. PVGIS notes that "the performance of PV modules depends on the temperature and on the solar irradiance", and that if air movement behind the modules is restricted they can get considerably hotter. A tight, flat layout is therefore a little less efficient than an airy one.
- Shading. PVGIS's built-in horizon estimates "the effects of shadows from nearby hills or mountains". Roof plant, parapets, roof lights and neighbouring buildings are not part of that terrain calculation, so they need their own analysis; the shading guide covers the method.
- Losses and age. The 14% system loss covers cables, inverters and dirt. PVGIS adds that modules "tend to lose a bit of their power" over the years, so average output across a system's life is "a few percent lower than the output in the first years".
- Weather. One standard deviation of year-to-year variation is 2.6% to 3.5% of the annual figure in these cases, so any single year can sit above or below the averages shown.
How do you scale from one panel to a system?
Multiply panel wattage by panel count to get kWp, then multiply by the yield. For 400 panels of 600 W on east-west rows in Manchester, that is 400 × 0.6 = 240 kWp, and 240 × 740.72 = 177,773 kWh a year. One panel (444 kWh a year) multiplied by 400 gives the same answer.
Wattage changes the panel count, not the yield per kWp. A 600 W panel makes a third more than a 450 W panel in the same place and layout, but the same system output needs a quarter fewer 600 W panels. Whether the larger module suits the roof, the rails and the lifting plan is a separate question. How many kWp a building should carry is set by its demand, not by one panel's output, and that method is in the sizing guide. Turning kWh into a bill saving is what the savings calculator does.
Which settings produce these numbers?
- Tool: PVGIS 5.3, PVcalc grid-connected fixed system, run in October 2026. The manual says "the current default version is PVGIS 5.3".
- Radiation data: PVGIS-SARAH3 (2005 to 2023), with ERA5 for other weather variables and the calculated horizon switched on.
- Panels: crystalline silicon, 1 kWp, 14% system losses. Azimuth 0 (south) at 35 degrees and at 10 degrees, and azimuth -90 (east) and 90 (west) at 10 degrees, averaged for the east-west case.
- Scaling check: a 0.55 kWp run for Birmingham returned 532.43 kWh a year, and multiplying the 1 kWp figure (968.06) by 0.55 also gives 532.43.
The limits matter. The runs use coordinates near each city centre, so a site on a hill or in a valley can differ. PVGIS does not make specific calculations for bifacial modules, and a flat 14% loss factor stands in for a specific inverter, so the figures show no inverter clipping. They are first-year modelled values, not measurements. PVGIS also offers a newer crystalline silicon coefficient set that its manual says gives a 2 to 3% gain in annual energy yield; these runs use the default setting. For a roof-specific number the check is a designer's model that uses the real layout and shading, and you can send an enquiry through the site's form for a contractor to run one. The wider specification is set out in the commercial PV systems guide.
Sources
- PVGIS user manual, European Commission Joint Research Centre, pvgis-user-manual, checked 22 October 2026.
- PVGIS 5.3 PVcalc runs (PVGIS-SARAH3, crystalline silicon, 1 kWp, 14% losses), European Commission Joint Research Centre, checked 22 October 2026: Plymouth south 35°, south 10°, east 10°, west 10°; Birmingham south 35°, south 10°, east 10°, west 10°; Manchester south 35°, south 10°, east 10°, west 10°; Glasgow south 35°, south 10°, east 10°, west 10°; and Birmingham at 0.55 kWp, south 35°.
Common questions
How much does a commercial solar panel produce per day?
It depends on place, layout and season. A 550 W panel on a south-facing 35 degree roof in Birmingham averages 1.46 kWh a day over a year, from 0.59 in December to 2.15 in June (PVGIS). On east-west rows the yearly average is 1.21 kWh a day.
Is a 600 W panel producing 600 W all day?
No. The 600 W label is a test-condition figure, and output follows the light. In the PVGIS hourly data used on the kWp page, the best hour of 2023 for a south-facing 35 degree array in Birmingham delivered 885 W per kWp, which would be about 531 W from a 600 W panel.
Do panels still produce on cloudy days?
Yes, at lower output. PVGIS notes that a large fraction of the radiation reaching the ground is scattered by the sky, clouds and haze rather than coming directly from the sun. The monthly averages above already include UK cloud, so they are not clear-sky figures.
How much more does a 600 W panel make than a 450 W one?
A third more per panel, in the same place and layout, because output is proportional to rated power. Per kWp the two are identical, so the larger panel changes how many modules a system needs rather than how much a kWp produces.