How many solar panels do I need for my home?

• The average 1-2 bedroom home needs 4-6 solar panels
• The average three-bedroom home needs 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

How many solar panels do you need for your home? (pic credit Solar Fast)

If you’re thinking about installing solar panels, the first question is usually, “how much do solar panels cost?” A valid one, but a more important one is, “how many do I need?”, because the answer to this question impacts the former.

The more you add, the higher the cost, so it is important to strike the right balance to actually meet your needs.

The answer depends on a few factors including:

1. The size of your home
2. Your annual electricity consumption (measured in kilowatt-hours or kWh).
3. The efficiency of the solar panels you intend to have installed, and;
4. How many hours of daylight you get where you live.

Don’t worry, you don’t need to be an expert in all of this to work our how many panels you’ll need. Your solar panel installer will do the hard parts for you, but here’s a rough guide based on the size of your house:

Our calculator tool further down the page will help you work out:

• how many solar panels you’ll need;
• how much your installation is likely to cost;
• how much you’ll be likely to save on your annual energy bills, and;
• how quickly you’ll break even on your solar investment.

How many solar panels do you need for your 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 power to cover 49% of the average household’s annual electricity 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 15.46 years, according to our calculations.

The 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.

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 is 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 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 how 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.

If you want to do this manually (to sense check our calculator), these are the steps you need to follow:

1. Calculate your annual electricity usage. You can get this information from your fuel bills for the last 12 months.
2. Work out the number of panels needed. To do this, divide your total electricity consumption from step 1 by 265 (where 265 kWh is the typical output of a 350W panel). 
3. Calculate how big your roof is. You can get a professional to do this or estimate it based on the top floor area and times by 1.2. However, note that this will only give you a ballpark figure. 

We’ll go through these steps in more detail below.

1. Calculate your annual electricity usage

The first step is to determine how much electricity you use yearly.

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 how much electricity you use by checking your energy bills.

If you don’t have an annual summary or the past 12 months’ bills, 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. Here’s a rough overview table of what you should expect to see.

*Please note that these numbers are rough estimates. Your actual home’s energy needs may vary.

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.

Here’s a general idea of how much space different sized solar panel systems take up (in square metres – m2):

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

3. Find out how big your roof is

So far, so good. But before you can move on, you’ll need to know you have enough roof area to actually accommodate the solar panels. 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.

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

Considering these factors, you can roughly estimate how many panels you need—though, of course, a trained professional should give the final estimate.

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 – how many hours of sunlight you can expect in a year;
• Direction and orientation of your roof – does the pitch of your roof face north, south, east or west?;
• Available “useful” roof area – a complex roof (different pitches, cross-gables, etc.) or a roof with many obstructions (like chimneys) can limit the number of solar panels you can install;
• Construction of roof and ability to carry the weight of solar panels – this includes the roof’s condition, age, etc., to ensure it can support the panels;
• Type of solar panels;
• Solar panel efficiency, and; 
• Other factors – including shading from nearby buildings, trees, chimneys, local permitting/listed building/protection area restrictions.

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 generate.

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.

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

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 square metres and are rectangular.

They’re usually about 2 metres long and 1 metre wide, and they have 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.

To give you a rough idea, here are some average dimensions of typical solar panels available in the UK.

*Note that different brands may have varying dimensions for their solar panels, so it’s important to take this into consideration.

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 HIT N340, measuring 1.7 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.

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.