More homeowners are switching to solar across the UK, with national statistics showing a total of 16.9 GW of solar capacity across 1,595,916 installations as of June 2024.
Before making the switch, you first need to determine how many solar panels you need to power your house. This can ensure you generate enough free electricity to meet your needs and maximise efficiency and savings.
This guide explores various factors you need to consider to make an informed decision about the number of solar panels you need to power a house in the UK.
Quick Takeaways:
- The number of solar panels you need to power your house will depend on your energy usage, the size of the solar array, and your roof.
- Other factors like your location, roof orientation, and the type of solar panel you choose can also impact the number of solar panels you need.
How Many Solar Panels Do I Need to Power Your House?
The number of solar panels you’ll need to power your house will vary depending on various factors. These include:
Your Electricity Usage
The first thing you need to do is determine how much electricity your home uses yearly. An easy way to do this is by checking your past electricity bills.
For example, according to Ofgem, the typical average electricity usage for a 2–3-bedroom house is 2,700 kWh annually.
Your electricity bills will give you a more accurate figure since every home’s usage can vary based on factors like your home’s size, the number of people living in the home, and the energy efficiency of the house and your appliances.
The Size of the Solar Array
Understanding solar array sizes is crucial for optimal energy generation. Incorrect sizing can result in spending more than necessary or ending up with a system that can’t meet your needs.
Domestic solar panel sizes in the UK usually range from 250 to 400 watts with an average of 350W. The following formula can help you work out the solar array size you require:
Array size (kWp) = Panel Output (W) x Number of Panels
According to the Energy Savings Trust, the average solar panel system is around 3.5 kilowatt peak (kWp).
3.5kWp = 350 x 10.
Therefore, you would need 10 solar panels with an output of 350W to get a 3.5kWp solar system array.
The Size of Your Roof
The size of your roof will determine how many solar panels you can install. It’s essential to work out the amount of space on your roof that you can actually put solar panels on.
Not all parts of the roof will have the ideal installation angles or orientation for solar panels, thanks to things like dormer windows, vents, and chimneys.
The Energy Savings Trust notes that most panel systems typically cover an average roof surface area of between 10 to 20m2.
You can hire a professional to check your roof or check your building plans to see if you can fit the number of solar panels you need.
If the roof is small, you may need to use fewer panels with higher power ratings or add them to a different area, like the shade or garden.
Other Factors That Can Affect How Many Solar Panels You Need
Other factors to consider include:
Location
The geographical location of your house will determine how many hours of sunlight your panels receive.
The UK has an average of 4-5 hours of sunlight per day, with a modest 2.5 hours of peak sunlight. Peak sunlight hours will vary by location, with some areas receiving more light than others.
You may need to install more solar panels to capture as much sunlight as possible if your location has limited sunlight hours.
Roof Angle and Orientation
Your roof angle and orientation can impact energy generation by determining the panel’s exposure to sunlight.
In the UK, south-facing roofs get the most exposure to sunlight, allowing your panels to produce more electricity than those on roofs facing east, west, or north.
You may need to install a few more panels on east or west-facing roofs to achieve the same results.
When it comes to angles, you can achieve fair results with a pitch of anywhere from 20o to 50o, with averages of 35o giving the best results.
Type of Solar Panel
Solar panels come in different types, each having its own efficiency range. The varying efficiency levels can impact the number of panels you need depending on the type you choose.
The two main types of solar panels for residential installations are:
- Monocrystalline panels – These are the most efficient type of panel available, with an efficiency range of between 18% and 24% on average. They’re suitable if you need the highest possible efficiency due to a suboptimal geographical location or limited roof space. However, they’re the most expensive.
- Polycrystalline panels – These have a lower efficiency of between 13-17% on average but are a cheaper option than monocrystalline panels.
If you’re installing polycrystalline panels, you’ll need more of them to achieve the same result as monocrystalline panels. However, they can be a cost-effective solution if you have a more extensive roof to work with.
How Many Solar Panels Do You Need to Power a House Off-grid?
It may not be possible to power your house using solar panels entirely off-grid because there will be periods when there is no sunlight, such as at night or during the winter.
Solar installations in the UK are usually designed to subsidise your energy requirement and reduce your reliance on the grid instead of replacing it.
You can choose to add battery storage to store the energy you can use instead of grid electricity when there is no sun. However, it may not be enough to meet your needs throughout the night.
Your solar panels may also be incapable of generating enough power to recharge the battery during the winter due to limited sunlight availability.
Going completely off-grid will require more considerations, such as a higher power system, extra costs, and more roof space to accommodate more solar panels.
Final Thoughts
Choosing the correct number of solar panels to power your house can seem like a daunting task, but you can make an informed decision by considering the above factors.
Also, ensure you consult a professional MCS-certified installer who can offer a detailed assessment and help you determine how many solar panels you need based on your situation.
Sources and References:
- https://www.gov.uk/government/statistics/solar-photovoltaics-deployment
- https://www.ofgem.gov.uk/average-gas-and-electricity-usage
- https://energysavingtrust.org.uk/advice/solar-panels/