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Solar Panel Output: How Much Electricity Do They Produce?

A solar panel's power output is measured in kilowatts (kW)

A three-bedroom house will typically need a 3.5 kilowatts peak (kWp) system

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Investing in solar panels can be daunting if you’re not familiar with the lingo – there are a plethora of solar-specific definitions, energy is measured in all sorts of ways, and don’t get us started on the robotic, consonant-packed panel names.

Solar panel output can also come under this bracket of daunting jargon, but we’re here to make it easier for you.

We’ve compiled all the need-to-know things when it comes to making sure you have the right amount of power flowing out of your panels.

If you’re already familiar with all things solar, why not dive in and get yourself a quote for a new solar panel system? We can make this process a million times easier with our simple comparison tool.

Once you’ve filled in a few details, our suppliers will be in touch with quotes for you to compare. You’ll find the right deal in no time.

two men install a solar panel system

What's on this page?

Solar panel power output

Let’s start off with the basics – 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.

So, for example, a home in Cambridge typically receives four hours of sunshine a day. If this home has a 280-watt solar panel, it will generate 1,120 watt-hours (Wh) or 1.1 kilowatt-hours (kWh) of electricity that day (280 x 4).

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).

Take a look at the table below to compare the most powerful panels on the market – although you should be aware that high-power panels aren't necessarily for everyone. There are some excellent all-rounders out there, and our guide on the best solar panels will give you a better idea of which panel is best for you.

CompanyModelSolar panel power
SunPowerMaxeon 3400W
Solaria PowerXT Pure Black400W
SunPowerMaxeon 3 BLK375W
SunPowerX-Series X22370W
Project SolarEVO Ultramax345W
PanasonicHIT® N340340W

How much power output does your home need?

This all depends on two things: how much electricity you use, and 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 – around 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 four 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
850 kWh
14 sq. metres
1,700 kWh
21 sq. metres
2,550 kWh
28 sq. metres
3,400 kWh

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).

We know that working this out for your home’s specific needs can be enough to give you a headache. So let us take the reins and do the maths for you. All you have to do is pop a few details in this form to receive free quotes tailored to you and your family’s needs.

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, the table below shows 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
425 hours
2,550 hours
3,400 hours
850 hours
850 hours
5,100 hours
6,800 hours
1,700 hours
1,275 hours
7,650 hours
10,200 hours
2,550 hours
1,700 hours
10,200 hours
13,600 hours
3,400 hours

The average 3.5kW south-facing domestic solar PV system will produce about 3,000kWh per year (8.21kWh per day).

What affects how much electricity a solar panel can generate?

If conditions aren’t ideal, your solar panels’ efficiency will take a hit, meaning they won’t be able to work at their maximum power output.

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.


Make sure your solar panels are installed out of the shade, in direct sunlight. If just a small amount of shade covers a solar panel, it can significantly reduce how much electricity it’s able to generate.

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.


Make sure you regularly clean your solar panels with a damp cloth and soap. 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.

How will you know how much electricity your solar panels generate?

solar panel meterYour 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 means you’ll be able to see how much power your solar panels are generating with the click of a button on your computer or phone.

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

Feeling more clued up on solar panel output? Well then, perhaps now’s the time to make the switch to solar.

After all, a majority of people want to go solar, according to our National Home Energy Survey.

Plus, just like we’ve simplified solar in this article, we can make the comparison stage easier for you too!

The only thing you need to do is put a few details in our easy-to-use comparison tool – then put your feet up and let us do the hard work. We’ll pass on your information to our suppliers, who’ll then be in touch shortly with free quotes for you to compare. You’ll be reaping the solar-powered rewards in no time!

Beth Howell Senior Writer

Beth has a real passion for green living. She’s been absorbed in eco research for over three years, and has become quite the expert. Whether you’re after a new set of solar panels, a home energy improvement, or you want to catch the latest eco news, she’s got your back.

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