How Many Solar Panels Do I Need?

The number of solar panels you'll need to power your home will depend on how much electricity your household uses. As a rule of thumb, the more electricity you use, the more solar panels you'll need.

Most UK households need between 4 and 16 solar panels installed on their roof, but you can work out exactly how many solar panels you'll need using some basic maths.



How Many Solar Panels Are Needed to Run a House?

It’s all going to depend on your household’s electricity usage. A large 4 bedroom detached house will use a lot more electricity than a small 1 bedroom bungalow. As a rule of thumb, the more electricity you use, the more solar panels you’ll need to cover your home’s electricity usage.

The table below provides you with a very rough estimate of how many solar panels you’ll need, based on the size of your household and how much electricity you use:

Household Size
Annual Electricity Usage
Number of Solar Panels
1 person
850kWh
4
2 people
1,700kWh
8
3 people
2,550kWh
12
4 people
3,400kWh
16


To get a more accurate estimate of how many solar panels you need, you’ll need to follow 4 simple steps that involve you doing a bit of maths - but nothing so complicated that it will leave you scratching your head! The 4 steps to working out how many solar panels you need are:

  1. Calculate your daily electricity usage
  2. Work out the average daily sunshine hours
  3. Figure out the daily electricity output of a solar panel using sunshine hours
  4. Divide the electricity output of a solar panel by your daily electricity usage

Read on to find out how to complete these 4 steps, with a worked example throughout.



How Many Solar Panels Do I Need?

how many solar panels do I need

1. Calculate Your Daily Electricity Usage

To find out how much electricity your home uses, take a look at your past energy bills. These will show you how much electricity you’ve used in kilowatt-hours (kWh) over a period of time depending on how frequently you’re billed (every month or quarter, for example).

To work out how many solar panels you’ll need to power your home, you first need to calculate your electricity usage per day. If you’re billed monthly, you’ll need to divide your electricity usage in kWh by 30; if you’re billed quarterly, you’ll need to divide the figure by 90, and so on. A UK home with a monthly electricity usage of 320kWh, for example, will use about 11kWh of electricity each day (320 / 30).


2. Work Out the Average Daily Sun Hours in Your Location

Next you’ll need to work out the average number of sunshine hours per day where you live. This information is pretty hard to get hold of, but luckily the Met Office have calculated the average daily sunshine hours for each month in the UK, so you won’t have to sit outside and count them yourself! The figures are shown below:

  • January: 2 hours per day
  • February: 3 hours per day
  • March: 4 hours per day
  • April: 6 hours per day
  • May: 6 hours per day
  • June: 7 hours per day
  • July: 7 hours per day
  • August: 6 hours per day
  • September: 5 hours per day
  • October: 4 hours per day
  • November: 3 hours per day
  • December: 2 hours per day

Obviously the number of daily sun hours varies each month, so it’s best to take an average for the year. Based on the above figures, the home used in the previous example gets about 4.5 hours of sunshine per day throughout the year in the UK.


3. Figure Out the Daily Electricity Output of a Solar Panel using Sunshine Hours

Once you’ve figured out the average number of sunshine hours your home receives per day, you can then work out how many solar panels you’ll need. This will depend on the wattage of the solar panels you choose. The wattage determines how much electricity a solar panel can produce. Solar panels range in size from about 240 watts up to 370 watts per panel.

To calculate how much electricity a solar panel generates, you’ll need to use the following multiplication: sunshine hours per day x solar panel wattage.

A mid-range solar panel is about 300 watts, so we’ll use this in our example. Based on a UK home getting around 4.5 hours of sun a day, a 300-watt solar panel would produce 1,350 watt-hours or 1.35kWh of electricity per day (4.5 x 300).


4. Divide the Electricity Output of a Solar Panel by Your Daily Electricity Usage

To work out how many solar panels your home needs to cover 100% of its electricity usage*, you simply need to to divide your daily electricity usage by the daily power output of a solar panel (both in kWh). So based on our example, if a home used 11kWh of electricity per day, it would need to install about 8 300-watt solar panels to generate enough power (11 / 1.35).

Good to know: the higher the wattage of the solar panels you install, the fewer you’ll need to cover your electricity usage. Using the example above, if the same household installed 240-watt solar panels instead, they’d need about 10 solar panels to generate the same amount of electricity.


*If you only want your solar panels to subsidise part of your home’s electricity usage, you can install a smaller number of solar panels. Based on the example above, if this household wants solar panels to cover just 70% of their home’s electricity usage, they’d only need 6 solar panels (11 / 1.35 x 0.7).

Working your way through these steps will provide you with an indication of how many solar panels you’ll need to install to power your home. If you want to find out how much solar panels cost, visit our solar panels prices page. To get a free quote from an expert solar panel installer in your area, just fill in the form at the top of the page to arrange a home survey.

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