✔ A solar panel’s power output is measured in kilowatts (kW)
✔ A three-bedroom house will typically require a 3.5kWp solar panel system
✔ Complete the form above to receive free solar panel quotes from our trusted suppliers
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Solar Panel Power Output
A solar panel’s output is expressed in watts. On average, a domestic solar panel has a power output of around 265 watts, although it can range anywhere from as little as 225 watts to more than 350 watts. The higher the wattage of a solar panel, the more electricity it can produce under the same conditions.
To calculate how much electricity a solar panel will produce in a day, you simply have to multiply its wattage by the number of sunlight hours.
For example, a home in Cambridge with a 280-watt solar panel that receives 4 hours of sunshine will generate 1,120 watt-hours (Wh) or 1.1 kilowatt-hours (kWh) of electricity that day (280 x 4).
In contrast, if that same home had a 320-watt solar panel, it would be able to produce 1,280Wh or 1.2kWh of power on that same day (320 x 4).
The table below shows you the solar panel power output range for some of the best solar brands.
Solar Panel Power
275 to 365 watts
290 to 365 watts
245 to 330 watts
256 to 360 watts
280 to 300 watts
250 to 360 watts
How much power output does your home need?
This all depends on a) how much electricity you use, and b) how much of your home you want your solar panels to power.
If your household has a particularly high energy usage or you want to solely rely on solar panels to power your home, we’d recommend getting solar panels with a high output – around 300 watts (per panel) or more.
However, if you don’t use much electricity day-to-day, or only want solar panels to subsidise some of your home’s energy usage, you can choose solar panels with a lower output – of about 225 to 275 watts.
Most homes will install several solar panels, known as a solar panel system. A typical 3-4 bedroom house will require a 3-4kWp solar panel system, typically composed of 12-16 solar panels.
The output of a solar panel system can be calculated by multiplying the wattage of each solar panel by the total number of solar panels. For example, a home in Reading with 4 250-watt solar panels would have a 1 kilowatt (kW) solar system (250 x 4).
Most domestic properties have between a 1kW and 4kW solar panel system, depending on how much power they need and the size of their roof. The table below shows you how much electricity different sized solar systems normally generate over a year, as well as how many solar panels they’re typically made up of:
Solar Panel System Size
Number of Solar Panels
Required Roof Space
Annual Electricity Output
8 sq. metres
14 sq. metres
21 sq. metres
28 sq. metres
Top tip: to work out how big your solar panel system needs to be, take a look at your latest energy bill. This will show you how much electricity you have used in kWh in the last month (or however often you’re billed).
How much energy does a solar panel produce?
Typically, a 3kW or 4kW solar panel system will produce enough energy for a family-sized home of 3 to 5 people, while a 1kW or 2kW solar panel system will be about the right size for a couple or single occupant.
To give you an idea of just how much electricity solar panels can generate, we’ve put together the table below. This gives you an example of how many hours you can use a selection of household appliances for, based on how much electricity different sized solar panel systems normally produce in a year.
Solar Panel System Size
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What affects how much electricity a solar panel can generate?
A solar panel won’t be able to work at its maximum power output all the time if conditions aren’t ideal. There are several factors that can impact how much electricity a solar panel is able to generate. These include:
- Direction and angle of your roof: a solar panel works at its best when installed on a south-facing roof at a 35-degree angle. However, solar panels can still produce a decent amount of power on an east-facing or west-facing roof, and at an angle anywhere between 10 and 60 degrees.
- Shade: if just a small amount of shade covers a solar panel, it can significantly reduce how much electricity it’s able to generate. Make sure your solar panels are installed out of shade in direct sunlight.
- Time of the year: a solar panel will produce more power in the summer months when the days are longer and there are more sunshine hours. If it gets too hot, however, solar panels can overheat; in temperatures over 25°C, they’ll generate a lot less power.
- Dirt: if a solar panel is covered in debris, its power output will fall because sunlight will be stopped from hitting the panel. Although it rains a lot in the UK, don’t rely on it to wash away any dirt. Make sure you regularly clean your solar panels with a damp cloth and soap.
How will you know how much electricity your solar panels generate?
Your solar panels will come with a meter that will be placed in an accessible location within your home. This meter will record the amount of electricity being produced by your solar panels.
Some solar brands are also rolling out online monitoring tools which allow you to view how much power your solar panels are generating via your computer or smartphone app.
As solar panels require virtually no maintenance, it can be easy to forget about them once they’re installed on your roof. We’d recommend checking them regularly, however, to ensure they’re clean and in good condition.
It’s worth monitoring your meter frequently too, to make sure they’re generating the expected amount of power. If your solar panels’ power output is particularly low, it could be a sign of a problem.
Finding an installer
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