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How much do you lose to clipping?
Plug-in inverters stop at 800 W. Put in your panels, the way they face and their angle, and see how much the limit cuts off, month by month, and how much extra the bigger panels still make.
- lost by 2,000 Wp on a garden stand in Birmingham
- 16%
- a year from 1,000 Wp instead of 800 Wp
- +191 kWh
- lost by 2,000 Wp hung upright
- 10%
Lost to the 800 W limit
2.2%
27 kWh of the 1,207 kWh a year your panels could make
- Output after clipping
- 1,181 kWh
- Extra over 800 Wp of panels
- +414 kWh
The extra 460 Wp of panels keeps 94% of what it makes. The rest is cut off on bright middays.
Month by month
| Month | Output | Clipped |
|---|---|---|
| Jan | 44 | 0 |
| Feb | 62 | 0 |
| Mar | 101 | 3 |
| Apr | 130 | 6 |
| May | 146 | 5 |
| Jun | 148 | 3 |
| Jul | 145 | 6 |
| Aug | 133 | 1 |
| Sep | 109 | 3 |
| Oct | 76 | 0 |
| Nov | 50 | 0 |
| Dec | 38 | 0 |
Other panel sizes here
| Panels | Clipped | Output | Extra over 800 Wp |
|---|---|---|---|
| 800 Wp | 0% | 766 kWh | +0 kWh |
| 900 Wp | 0% | 862 kWh | +96 kWh |
| 1,000 Wp | 0.1% | 957 kWh | +191 kWh |
| 1,260 Wp | 2.2% | 1,181 kWh | +414 kWh |
| 1,600 Wp | 7.9% | 1,412 kWh | +646 kWh |
| 2,000 Wp | 16% | 1,615 kWh | +849 kWh |
PVGIS hourly solar data near Birmingham, facing south at 30°, with no shading. Hourly averages smooth out short bright spells, so real clipping can be a little higher.
Worked examples
Clipping by panel size in Birmingham
Share of output lost to an 800 W inverter, and the kWh a year gained over 800 Wp of panels, facing south. The sizes are the kits we track, plus 1,600 and 2,000 Wp.
| Panels | Garden stand (30°) | Flat roof frame (15°) | Railing or wall (upright) | Kits at this size |
|---|---|---|---|---|
| 800 Wp | 0% clipped766 kWh a year | 0% clipped722 kWh a year | 0% clipped566 kWh a year | |
| 890 Wp | 0% clipped+86 kWh a year | 0% clipped+81 kWh a year | 0% clipped+64 kWh a year | |
| 920 Wp | 0% clipped+115 kWh a year | 0% clipped+108 kWh a year | 0% clipped+85 kWh a year | |
| 930 Wp | 0% clipped+125 kWh a year | 0% clipped+117 kWh a year | 0% clipped+92 kWh a year | |
| 1,000 Wp | 0.1% clipped+191 kWh a year | 0% clipped+180 kWh a year | 0% clipped+142 kWh a year | |
| 1,030 Wp | 0.2% clipped+219 kWh a year | 0% clipped+207 kWh a year | 0% clipped+163 kWh a year | |
| 1,040 Wp | 0.2% clipped+228 kWh a year | 0% clipped+216 kWh a year | 0% clipped+170 kWh a year |
|
| 1,260 Wp | 2.2% clipped+414 kWh a year | 1.2% clipped+401 kWh a year | 0.7% clipped+319 kWh a year | |
| 1,600 Wp | 7.9% clipped+646 kWh a year | 5.8% clipped+638 kWh a year | 4.3% clipped+518 kWh a year | No kit we track |
| 2,000 Wp | 16% clipped+849 kWh a year | 13% clipped+854 kWh a year | 10% clipped+703 kWh a year | No kit we track |
Gains are against 800 Wp of panels on the same mounting. Output is after the 800 W limit, with no shading, from PVGIS 5.3 hourly data for the region and monthly totals for Birmingham. Prices are the cheapest in stock, . See every kit in stock.
Through the year
Clipping happens on summer middays
An inverter only clips when the panels make more than it can pass on. With the sun high and the sky clear, a big array goes over 800 W for a few hours around midday. The rest of the time, and most of the winter, it doesn’t get near.
That’s why oversizing pays. The extra panels make more every morning, evening and cloudy day, and only give some of it back on the brightest days. The table shows the kWh lost each month to an 800 W inverter for two kits on a south-facing stand in Birmingham.
Steeper panels clip less. A panel hung upright on a railing faces the low winter sun well but catches the high summer sun at an angle, so it seldom reaches its peak. See the best angle for your panels.
| Month | 1,260 Wp | 2,000 Wp |
|---|---|---|
| Jan | 0 kWh | 1 kWh |
| Feb | 0 kWh | 11 kWh |
| Mar | 3 kWh | 29 kWh |
| Apr | 6 kWh | 45 kWh |
| May | 5 kWh | 43 kWh |
| Jun | 3 kWh | 43 kWh |
| Jul | 6 kWh | 45 kWh |
| Aug | 1 kWh | 30 kWh |
| Sep | 3 kWh | 30 kWh |
| Oct | 0 kWh | 12 kWh |
| Nov | 0 kWh | 7 kWh |
| Dec | 0 kWh | 5 kWh |
| Year | 27 kWh | 301 kWh |
The rules
How big can the panels be?
The 800 W limit is on the inverter’s output, not on the panels.
800 W
Inverter output
The most a plug-in kit may feed into a socket circuit (SI 2026/848, Explanatory Memorandum para 5.1).
960 Wp
Wiring advice
Above this, the maker must advise you to consider a check of your wiring (IPS §4.1).
Microinverters also have a limit for each panel input. Check that each panel suits its input on the inverter’s datasheet before adding bigger panels. Our compatibility checker runs the numbers.
Clipping and oversized panels: questions
What is inverter clipping?
A plug-in kit’s inverter can put out no more than 800 W. When the panels could make more than that, on a bright midday, the inverter holds its output at 800 W and the extra is lost. That lost energy is clipping.
How much do I lose putting 2,000 Wp of panels on an 800 W inverter?
About 16% of what the panels could make, facing south on a 30° stand in Birmingham: 301 kWh a year. Hung upright on a railing or wall the loss falls to 10%, because upright panels rarely reach their peak. Even after clipping, 2,000 Wp makes 849 kWh a year more than 800 Wp on the stand.
Is it worth buying more panel watts than the 800 W limit?
Usually yes. Extra panels make more in the mornings, evenings and dull weather, when the inverter has room to spare. In Birmingham on a south-facing stand, 1,000 Wp makes 191 kWh a year more than 800 Wp and loses 0.1% to clipping. The returns fall as you add more: the extra panels in a 2,000 Wp kit keep 74% of what they make.
When in the year does clipping happen?
In spring and summer, around midday. For 2,000 Wp on a south-facing stand in Birmingham, most is lost in Apr.
What is the most panel power a plug-in kit can have?
The government’s product specification for plug-in solar caps the panels at 2,000 W DC. Above 960 W, the manufacturer must advise you to consider having your wiring checked.
Why might real clipping be higher than this?
We work from PVGIS hourly averages. Within an hour, sun breaking through cloud can push panels above their usual peak for a few minutes, and those short bursts get clipped too. Cold, clear spring days can do the same. So treat these figures as a floor, not a ceiling.
Sources
Free tools
Plan the rest of your setup
- CalculatorOutput, savings and payback for your home
- Kit finderThree answers, a shortlist of kits in stock
- Shade plannerDraw your horizon, see what shade costs
- Best panel angleUpright, stand or flat: output by angle
- Will it fit?Which panels and kits fit your space
- What can it run?Which appliances 800 W of solar can power