How Many Solar Panels Do I Need For My Home?

✔ The average three-bedroom home will need 10 solar panels

✔ Your electricity usage will determine how many solar panels you need

✔ The efficient your solar panels are, the less of them you'll need

Solar panel costs are coming down, which is excellent news – after all, they can save you money, cut your carbon footprint, and protect you from energy bill hikes.

But you don’t want to make a mistake and get the wrong number of solar panels installed, particularly during a cost of living crisis.

This guide will help you work out how many solar panels your home needs – though getting it exactly right will still require the help of an expert.

If you want to find out how many solar panels your house would require, fill in this form to receive free quotes from trusted suppliers.

How many solar panels are needed for a house?

The average one-bedroom house needs six solar panels, a typical three-bedroom house requires 10 panels, and a five-bedroom house will usually need 14 panels.

In each case, the panels will produce enough electricity to cover 49% of an average household's annual usage – or more, if you don’t leave the house very often.

Annual electricity usage is measured in kilowatt hours (kWh).

1 kWh is how much electricity it would take to run a 1,000 watt (1 kW) appliance for an hour – so for example, if you had a 500 watt dishwasher, you would use 0.5 kWh in an hour of use.

Without a solar battery, around half of the electricity your panels produce will go unused by your home, because you won’t always be there to use it when it’s generated.

Not to worry, though – you can sell this extra power back to the National Grid via the Smart Export Guarantee (SEG).

The savings you’ll gain from the SEG and from not having to pay for expensive National Grid electricity mean you’ll typically break even in 15.1 years, according to our calculations.

How to calculate the number of solar panels you need

Work out the number of solar panels you need by finding out how much electricity you use per year, then dividing that figure by the 265 kWh that each 350-watt panel produces in a year in the UK.

Next, check your roof to see if it's large enough to fit this many solar panels, and to make sure it's not north-facing, as this will make it much less profitable to get panels.

These steps can be tricky – but fortunately, we’ve done the hard work for you.

Just fill in the solar panel calculator below with your house’s number of bedrooms and where you live, and we’ll tell you how many solar panels you’ll typically need.

1. Calculate your annual electricity usage

The first step is to look up how much electricity you use every year.

After all, if you were deciding how many loaves of bread to buy for the week, it’d be great to know how many sandwiches your household typically eats.

Thankfully, you can find out how much electricity you use by simply checking your energy bills.

If you don’t have an annual summary or the past 12 months’ bills, just contact your supplier, and a representative will let you know your yearly total in kilowatt hours (kWh).

Compare your electricity usage with the table above to get a rough idea of how many panels you’ll need to generate roughly the amount of electricity you use each year.

For context, a three-bedroom house typically uses 2,700 kWh per year, according to Ofgem.

2. Work out what size panels to use

A typical solar panel is rated at 350 W.

In the UK, it'll produce 265 kWh per year, on average.

That means if you divide your annual electricity usage by 265, you'll end up with roughly the right number of solar panels for your home.

For example, a household that uses 4,000 kWh per year can divide that usage by 265 to find out it needs 15 solar panels.

As a rule of thumb across the UK, your solar array will produce 760 kWh for every 1 kW of panels on your roof.

3. Find out if your roof is suitable

Check your building plans or hire a professional to measure your roof, to see if you can fit the panels you need up there.

Bear in mind that the average panel is two square metres, and that you shouldn't use panels on a north-facing roof. Read more on our page: North Facing vs South Facing Solar Panels.

If your roof is on the small side, don’t worry – you may be able to simply use fewer panels that all have a higher power rating. You can also add solar panels to a shed or mount them in the garden.

If you consider these factors, you can work out roughly how many panels you need – though of course, the final estimate should be given by a trained professional.

If you want to receive free quotes from some of these trained professionals, just fill in this quick form.

What other factors affect how many solar panels you need?

Besides electricity usage, a few other factors affect how many solar panels you need. These include:

• Geographic location
• Direction and orientation of the roof
• Type of solar panels
• Solar panel efficiency 

Geographic location

The geographical location of a property determines how many hours of sunshine you'll get, and  as a result how much electricity the solar panels will produce.

Solar panels still work on cloudy days, but they produce more electricity in direct sunlight. So, if you live in an area that doesn’t get a lot of sun, you might want to install more solar panels (if you can fit them).

To illustrate, let’s look at an example. A property with a set of 10 350 watt (W) solar panels would produce around 2,978 kilowatt hours (kWh) of electricity a year in southern England. The same system would produce 2,221 kWh in northern Scotland.

To achieve the same result by getting solar panels in Scotland as you would in southern England, you’ll typically need one to three more panels.

Direction and orientation of roof

In the UK, the best orientation for solar panels is facing south. This exposes them to the most hours of sunlight, which means they produce more electricity than panels that face east, west, or north.

Solar panels on east- or west-facing roofs produce 20% to 30% less energy than those on south-facing roofs, according to Endesa.

So, if you have an east- or west-facing roof, you might need to install one to three panels to achieve the same energy production.

Type of solar panels

Each type of solar panel has a different efficiency range, and panels with lower efficiency produce less energy.

The two main types of solar panels used in residential installations are monocrystalline and polycrystalline panels. Polycrystalline panels are 13%-16% efficient on average, whilst monocrystalline panels are 18%-24% efficient.

This means that if you’re installing polycrystalline panels, you’ll need more of them to achieve the same results as you would with monocrystalline panels.

Efficiency of solar panels

If you choose solar panels that are highly efficient, you’ll need less of them to meet your energy needs.

Why is that? It’s simple really, the more efficient a solar panel is, the more energy it will produce.

Solar panels are 20% efficient on average, but some models have achieved 24% efficiency.

So, if you’re considering getting solar panels that are 24% efficient, you might need less of them. This works out well for you, since the more efficient a solar panel is, the more expensive it tends to be.

How big is a solar panel?

The vast majority of residential solar panels are rectangular in shape, measuring approximately 2 square metres.

They’re usually about 2 metres long and 1 metre wide, with a thickness of 3-5cm.

However, some manufacturers have recognised the need for compact panels, which are ideal for households with small roofs – although, they come at a cost. If you’re looking for something particularly compact, check out:

• Sharp’s 258.4W NQ-R Series, measuring 1.29 square metres

• Panasonic’s 300W N300, measuring 1.54 square metres

• SunPower’s 370W X-Series X22, measuring 1.63 square metres

You can compare the price of differently sized solar panels on our solar panel cost page. You can also get around the issue of limited roof space with high-efficiency solar panels.

These premium panels are particularly good at converting sunlight into electricity, offering conversion rates of around 20-22% (the industry standard is closer to 18%).

Small solar panels

There are plenty of small solar panels you can use to power a variety of off-grid systems based on batteries – most commonly leisure vehicles like caravans and boats.

They wouldn’t normally be considered for houses, as the number of connections to create a reasonably sized array would increase the cost by too much.

Instead of the standard size of two square metres, these are typically four times smaller, at 0.5 square metres – though the power output is also smaller, naturally.

The 50W panel is a popular model among small solar customers, but you can get anything from a 10W panel to a 100W panel, depending on your needs.

The best attribute of small solar panels is their flexibility. You can use their different outputs and sizes to get exactly what you need for your battery.

Speaking of which, you'll need a solar battery if you want to save solar energy for later, instead of only using it while the sun's shining.

Large solar panels

Solar panels as big as 3.1 square metres are now available for domestic use.

Companies like Risen Energy produce panels this size that can generate up to 670W – around twice as much as a typical panel – which makes sense considering its size.

Large panels aren't necessarily any more efficient, and it can be complicated to fit them around obstacles on your roof, but they can look neater and more uniform.

You don't have to get large solar panels, even if you have a big roof or large off-grid building to power – but sometimes it makes more financial sense to go big for your home.

Of course, cost considerations also come into this calculation, and large panels are often prohibitively expensive.

That's why they're normally only produced for commercial use.

How heavy are solar panels?

Residential solar panels usually weigh between 18kg and 20kg.

That means a typical 10-panel solar array weighs more than two fully grown men, on average.

This is an excellent reason to hire a professional installer to get you all set up with solar power – along with the fact that they'll install the panels properly.

If you're buying solar panels for a vehicle or small off-grid building, you should consider flexible solar panels, which can bend around a corner or over a bump, and are also lighter, typically weighing in at between 0.8kg and 3kg.

Want to learn more? Head to our helpful guide How Much Do Solar Panels Weigh? for more information.

Next steps

You’re now armed with all the information and practical advice you need to work out roughly how many solar panels you need for your home.

That means you’re ready to approach a solar professional, tell them your electricity needs and roof size, and have an informed conversation about how many panels you’ll require.

If you’re ready to see how much solar panels would cost for your home, just fill in this form to receive free quotes from our trusted suppliers.

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