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How Many Solar Panels Do I Need?

solar panels on red house in sweden

The average three-bedroom home will need 10 solar panels

Solar panels typically cut your energy bills by £411 per year

You’ll break even within 12 years, on average

Solar panels 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.

Getting too many is an unnecessary expense, and too few could make your purchase unprofitable – or lead you to pay your installer to put up more panels another time.

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 to power 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.

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

1 kWh is how much electricity it would take to power 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.

Household SizeAnnual Electricity UsageNumber of
Solar Panels
Size of Solar
Panel System
1 bedroom1,800 kWh62.1
3 bedrooms2,900 kWh103.5
5 bedrooms4,300 kWh144.9

In each case, the panels will produce enough electricity to cover around 50% of a household's annual usage – or more, if you don’t leave the house very often.

Without a solar battery, around half of this energy 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 11.67 years, according to our calculations.

How to calculate the number of solar panels you need

Of course, your home isn’t typical – it’s specific and special, so the number of solar panels you’ll need won’t necessarily match exactly with our table.

It should be pretty close, but you’ll want an exact number.

You can work out this answer to a high degree of precision if you consider the factors listed below – 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.

1. Your annual electricity usage

The first step is to look up how much electricity you use every year, so you can get enough panels to generate that much power.

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.

They’ll measure your annual electricity usage in kilowatt hours (kWh). If you own a one-bedroom house, you can expect your total to be around 1,800 kWh, while three-bedroom households will typically use 2,900 kWh.

Compare your electricity usage with the table above to get a rough idea of how many panels you’ll need.

2. Your annual sunshine hours

The more sunshine you receive, the more electricity your panels will be able to produce – so you need to know roughly how much sunlight will shine on your roof throughout the year.

Different regions enjoy wildly different amounts of sunshine, with East Anglia taking in 490 hours more sunlight than North Scotland, per year – about 81 minutes more per day.

You can find out how much the sun shines on your home by checking data provided by the Met Office.

3. Put it all together

One you have this amount, you can work out how much electricity the average 350 watt solar panel would generate on your roof over a year.

If you live in the Midlands, for instance, you’ll receive 1438.2 hours of sunlight per year, which you can multiply by 350 watts to get 503,370 watt hours – or 503 kWh.

Take into account the fact that the average solar panel produces 85.25% of its potential output over its lifetime, and you have a final result of 429 kWh per solar panel, per year.

Divide your annual electricity usage by this total, and you’ve got the number of solar panels you’ll need.

For instance, if you use 2,900 kWh per year, you can divide that by 429 kWh to come up with a result of seven panels.

However, this would only be the case in an ideal situation, in which the sun shines at exactly the right angle on your panels – so don’t be surprised if a solar specialist assesses your home and recommends as many as 10 panels.

4. The size of your roof

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.

If your roof is too small for the number of average solar panels you need, don’t worry – you can just get above-average panels instead.

These calculations are 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 (twice), and we’ll tell you how many solar panels you’ll typically need.

How much electricity does your property use?

You can find out how much electricity your property uses from your energy supplier – either from a bill or by getting in touch with the company – and compare it with the table above to see whether you’re using more or less than the average amount.

As a rule, a one-bedroom house typically uses 1,800 kWh, a three-bedroom house will use 2,900 kWh, and a five-bedroom house uses 4,300 kWh.

But it’s also a question you should keep asking yourself.

Electricity prices are predicted to shoot up from 17.2p per kWh last year to 28p per kWh this year, according to Nimblefins – meaning this is a great time to cut down on your electricity usage.

Look into energy-saving measures like replacing your bulbs with LEDs, getting smart plugs so you can set schedules and switch off your items from anywhere in the world, and using smart power strips to make your energy usage more efficient.

We also recommend getting a free smart meter to track your usage and accurately report your electricity usage without you having to lift a finger.

This may also help you to save tonnes of greenhouse gases from being released into the atmosphere, as most of the average Brit’s six-tonne carbon footprint comes from domestic emissions.

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.

josh jackman
Josh Jackman Senior Writer

Josh has written about eco-friendly home improvements and climate change for the past three years. His work has featured on the front page of the Financial Times; he’s been interviewed by BBC Radio; and he was the resident expert in BT’s smart home tech initiative.

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