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Why get solar panels?

  • Generate free, green electricity
  • Reduce your electricity bill by up to 64%
  • Get paid for what you don't use

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 more efficient your solar panels are, the less of them you’ll need

Before getting a solar panel system, many people’s first question is “how much do solar panels cost?”, but an equally important question, and one that influences cost, is “how many solar panels do I need?”.

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, based on your electricity usage. We’ll also factor in the physical size of solar panels, as how many your get might be dictated by how you can fit on your roof.

We’ll also go into factors that might affect the number of solar panels you need, such as the angle and direction of your roof, and the efficiency of the solar panels you choose.

Once you’re done reading, you should have a good idea of exactly how many solar panels you need. If you’re still not sure, don’t worry. Once you choose a solar panel installer, they can help you make that decision by offering you their expert advise.

infographic showing number of solar panels needed based on house size

How many solar panels are needed for a house?

Household sizeSolar PV systemNumber of 350W panelsRoof spaceAnnual energy outputAverage cost

One-bedroom flat

1 kWp


6 m²

790 kWh


1-2 bedroom house

2 kWp


12 m²

1,590 kWh


3 bedroom house

3.5 kWp


20 m²

2,645 kWh


4-5 bedroom house

5 kWp


28 m²

3,700 kWh


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 14.6 years, according to our calculations.

Number of solar panels needed based on number of people in your home

How many people live in your home will affect your electricity usage, and can affect the number of solar panels you need.

A large four-bedroom home with only two full-time occupants, for example, might only need six to 10 solar panels, instead of 14, as less people will be using electricity.

Here’s an overview of how many solar panels you need per person:

  • One to two people: six solar panels
  • Two to three people: 10 solar panels
  • Four to five people: 14 solar panels
  • Over five people: 16+ solar panels

House size still plays a large role in determining how many solar panels you need, since a large house will still use more electricity than a small house, even if there aren’t many people in it. That’s why it’s best to base how many solar panels you need off of your electricity usage, as this will give you the most accurate estimate.

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 yearly output of a solar panel – in the UK that’s around 265 kWh per year for a 350-watt panel.

Here’ the formula:

Annual electricity usage (in kWh) ÷ 265 (kWh)

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.

This calculator is meant to give you a general idea of how many solar panels you need, but there are several factors that can influence how many solar panels you need, which we’ll get into in later sections.

For example, the size of your roof and ow many panels it can fit might dictate how many solar panels you ultimately get.

Solar panels on a north-facing roof will be exposed to less direct sunlight, and produce less electricity. This will make it much less profitable to get panels, as you might have to get more (if you can fit them) to make up for this.

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.

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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 how big your roof is

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

Here’s a general idea of how much space different sized solar panel systems take up:

Solar PV system size

Number of solar panels

Surface area

1 kWp


6 m²

2 kWp


12 m²

3.5 kWp


20 m²

5 kWp


28 m²

*based of the average solar panel size of two square metres.

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.

Want to get a better idea of what it’s like to own a set of solar panels? Check out our case study with Andrew, based in North Yorkshire. 

Andrew had a 3.95 kWh solar panel system installed in June 2022, which cost roughly £6,000. Despite electricity prices increasing around the world, Andrew’s panels are already saving him £32.93 on energy bills. He’s also projected to save around a tonne of CO2 a year with his panels.

Check out the full interview with Andrew to learn more about solar panels.

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?

Most residential solar panels measure around 2 squares metres, and are rectangular in shape.

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

The largest residential solar panels are as big as 3.1 square metres. 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.

However, 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.

The smallest solar panels are around 0.5 square metres, although these are typically reserved for 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.

However, some manufacturers specialise in compact panels 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 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, which means you might be able to get away with having fewer panels.

average solar panel dimensions

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.


You need 14 solar panels with a 350-watt power rating to produce 10 kWh per day in the UK, on average.

However, inconsistent weather conditions mean your panels will generate more electricity on some days, and less on others.

Sometimes you’ll have more power than you can use, in which case you’ll be able to sell the excess to the grid through the Smart Export Guarantee.

You can have too many solar panels, to the extent that it stops being cost-effective.

You’ll increase your profits if you buy more panels than you need, by selling excess electricity to the grid, but this isn’t as valuable as using that electricity – so you’ll push back your break-even point.

The average three-bedroom house needs 10 solar panels. Every extra panel on top of that will increase your break-even point by half a year.

How many solar panels can fit on a roof depends not just on the roof’s size, but its shape as well.

In the UK, the average roof size is 50 to 75 square metres. Roofs of this size could potentially fit 20 to 30 solar panels.

However, the presence of multiple chimneys, ridges, or electric equipment could limit the amount of solar panels a roof can fit.

This isn’t much of an issue, since the average three-bedroom house only needs around 10 solar panels to meet its energy needs.

To live off-grid, the average family requires around 16 solar panels, each with 350 W peak power output. But that’s only the case if you reduce your energy consumption by 40%, and have a solar battery and a heat pump.

To go off-grid whilst using the same amount of electricity as you normally would, you’d need around 26 solar panels. This is over twice the amount of panels recommended for an on-grid three-bedroom house.

Solar panels last 25 to 30 years, but that doesn’t mean that they stop working beyond that point.

They’ll still produce electricity after 25 to 30 years, but their efficiency will start to drop by 0.2%-0.3% each year. This is quite a small drop in efficiency, so technically, you can use your solar panels for a very long time.

Solar panels don’t necessarily have to go on your roof, even if that’s where most people choose to install them.

If you have a large sunny garden, you could opt for ground-mounted solar panels, or a solar panel pergola. You can also install solar panels on a shed, although these would typically need to be lightweight thin-film solar panels.

Written by:
josh jackman
Josh has written about eco-friendly home improvements and climate change for the past four years. His work has been displayed on the front page of the Financial Times, he's been interviewed by BBC One's Rip-Off Britain, and he regularly features in The Telegraph and on BBC Radio.
Reviewed by:
Tamara Birch, senior writer, The Eco Experts
Tamara has written about environmental topics for more than four years. This includes advising small business owners on cost-effective ways, like solar panels and energy-efficient products to help them become more sustainable. 
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