What Size of Solar Panel Do I Need?

Most residential solar panels have a size of between 1kW and 4kW as they qualify for the best feed-in tariff rate.

A 2kW system will take up approximately 14 sq m of roof space, while a 4kW will take up around 28 sq m. One square meter of solar panel could generate 150 watts of free power.

You can compare the prices of different sized solar panels offered by installers in your local area by entering your postcode in the form above.

Solar Panel Sizes

Solar panel sizes for homes

The government's feed-in tariff, referred to as a government grant for installing solar panels, pays out based on the amount of electricity your panels produce. Therefore choosing the right panel size is an important decision.

As the feed-in tariff pays out the best rate for solar panel systems under 4kW, typical residential solar panel system will be sized between 2kW and 4kW. As the table below shows,a bigger system size will typically cost more but deliver a higher output leading to a higher return on investment.

System Size
Approx. Roof Space
Typical Cost
Typical Annual Output
Typical Profit Over 25 Years
8 sq. m
14 sq. m
21 sq. m
28 sq. m

If your house has a large roof you may want to consider a system even bigger than 4kW.

While a 4.5 to 5kW system will qualify for a slightly lower feed-in tariff rate, the additional power produced may still deliver a higher return on investment over 20 years. The cost of a 5kW compared to a 4kW isn’t significantly higher as you will not need to pay any additional labour time, scaffolding costs etc.

That said, if your roof only has space for a system under 4.5kW, you will probably be better off sticking with a 4kW or lower system and cashing in on the higher feed-in tariff rate.

For commercial use

Commercial solar panel systems tend to be much larger than residential solar panels. These sizes have their own bands for feed-in tariff payments. The upper bracket for the feed-in tariff is a 5,000kW system.

Learn more about commercial solar panels

Size of solar panels

The vast majority of UK homes’ roofs have adequate space for solar panels. A typical 1kW system will require around 8 square meters amount of space, whilst a typical 4kW system will require around 28 square meters.

System Size
Number of Panels
Roof Area Needed
12.7 sq. m
14.3 sq. m
19.2 sq. m
24 sq. m
25.5 sq. m
28.7 sq. m

If you have too small a roof for the size of solar system you wish to install, you can buy more efficient panels which will take up less space. It’s important to note that higher efficiency tend to cost more (learn more).

The best thing to do is to discuss this with installers when they visit your home to provide a detailed quote.

Size of an individual panel

The size of individual panels will depend on your manufacturer. However, most brands have similar sized panels. A Yingli 48 Cell series, for example, has dimensions of 1310mm (L) x 990mm(W) x 40mm(H).

Learn more about how many solar panels your home will need

What size solar system do I need?

There are 3 factors to consider when determining which size of system is best for your home:

1. How much electricity you use
The more electricity you use, the bigger the system you will want in order to reduce your electricity bill by as much as possible. To find out how much electricity your home uses, check your bill statements.

2. How big your roof is
Obviously the size of your roof limits the size of the solar panel system you can have installed. The area where your panels will be installed also needs to be shade free for most of the day which could further reduce the amount of space available. Generally, the size of your roof should only be a concern if you have an abnormally small roof. Smaller roofs can install higher efficiency panels to make up for the lack of space although these panels cost more so its important to calculate your return on investment.

3. Your budget
The larger the system size the more it will cost. Whilst a bigger system will deliver a higher return on investment, your main concern should be whether you can afford it. Whilst a smaller system will generally deliver a lower return on investment, it’s important to remain within your budget.

You can use our calculator (see below) to work out exactly which size solar panel will suit your personal circumstances.

Solar panel sizing calculator

You can use our solar calculator to work out what size solar panel would be best for your situation. The calculator will show the savings, earnings and cost for each size of solar system available.

Click here for the calculator

Solar panel sizes and wattage

After you find out if your home is suitable to have solar panels fitted there are several things you then have to decide on to get the best performance from them. Firstly you should get an idea of the final voltage, amps and watts you want to create. You could decide this by doing a calculation as to how much energy your home gets through throughout a 24 hour period.

One square meter of solar panel could generate 150 watts of free power. The solar panel you are choosing must have the same types of cells in them as this will keep the power levels consistent. The larger the cell the more watts of electricity it will produce. The smaller ones do not produce as much so it is better to keep them all the same.

To work out for yourself the total power of a solar panel you should use this simple equation - Watts = Volts x Power. The voltage stays the same but the wattage changes with the size of the solar cells within the panel.

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