How Many Solar Panels Do I Need in the UK? | 2024 Guide

To calculate the number of solar panels you need, first determine your annual electricity consumption in kilowatt-hours (kWh). An average UK household consumes about 2,900 kWh annually.

Solar panels' output varies by model but assumes an average production of 400 watts (W) per panel under optimal conditions, with a lower estimate of 350W and a higher estimate of 450W.

Therefore, to cover a medium-low consumption profile for 2-3 bedroom houses (1,800kWh/year), you'd need approximately 4 to 8 solar panels, depending on whether they are 350W or 450W. For medium usage (2,700kWh/year), 8 to 13 panels would suffice. Households with medium-high consumption (4,100kWh/year) should consider 13 to 16 panels.

Keep in mind that these estimates are based on average conditions and actual needs may vary based on your location's sunlight exposure, the panels' efficiency, and your household’s energy consumption. As the number of residents increases, so do the energy consumption levels and solar panel sizes.

You can consult the table below for an idea of the number of solar panels required to power homes of different sizes.

The table gives a general estimate of how many solar panels you might need to offset your electricity use in the UK, but the exact number of panels will depend on several factors, including:

To calculate what solar system size you need, you should first know the amount of energy that you need to generate from your solar system daily. The other important things are the sun hours in your area and your roof space, as this can help you determine how many solar panels your roof can accommodate.

To find out how many you need to install on your roof, you should first check your monthly energy bills. Next, you will need to calculate the production ratio of your solar panels i.e., how much electricity your solar panel produces under the average sunlight and weather conditions in your area.

For the UK, the production ratio will be between 3.225Wh per day per Watt (W) on average. You can multiply this number by the Watts of solar panels. Consequently, for a 350 Watt panel, this would be 395.06kWh per day and 507.9kWh for 450W panels.

Finally, you should divide this number by the annual electricity usage, and it will show you how many solar panels you need. For the average 2 to 3 bedroom home this would be 2,700kWh consumed per day meaning that between 5 to 10 panels would be required on average.

It’s best to have more power than less, which is why you should round up the solar panels capacity for safety.

These can provide information on the amount of energy that you consume per day, and therefore how much energy you need your solar panels to generate daily. You can follow the same process to find the right commercial solar panel system size if you want to invest in solar PV for your business.

However, a roof is not the only option for installing solar panels. Ground-mounted arrays are another method of setting up your system. In the event of insufficient roof space can opt for garden solar panels if you have the space outside.

To determine the size of the panels that you need for your house, you need to know the following:

Most 1 bedroom and smaller 2 bedroom homes use 1,800kWh per year. In contrast, most larger 2 bedroom homes and 3 bedroom homes use 2,700kWh, which is the average household consumption in the UK. Larger homes tend to use an average of 4,100kWh annually.

Solar panels have variable efficiencies depending on the model or brand and the material they are made from.

Monocrystalline solar panels have the highest efficiency for domestic systems, tending to be between 15% to 24%, with experts listing the best solar panels as having above 20% efficiency at minimum.

Polycrystalline solar panels tend to have 13% to 16% efficiency while thin-film solar panels tend to have 7% to 13% efficiency. Polycrystalline panels tend to be the most common for domestic installations because of their superior performance.

South-facing roofs with a slight tilt towards the West perform the best in the UK. Countries such as Australia will require solar panels facing in the opposite direction. There are minute differences throughout the UK, but this rule generally applies throughout the region.

The optimum solar panel angle in the UK is between 30° to 50°. It is recommended to adjust the angles throughout the year to accommodate the changing position of the sun. Most roofs are perfectly suitable for solar panels unless they face North.

Similarly, flat roof solar panels are also an option when accompanied by ballasts. In fact, they can be easier to install and position at an ideal angle and orientation.

Certain factors can restrict how many solar panels your roof can hold.

Most roofs can easily manage 10kg per square meter, while the average weight load of a solar panel on a slanted roof is about 1.3kg per square meter (2.3kg per m2 on a flat roof). While they can weigh up to 18kg to 20kg, the force they exert per metre on a roof can be lower when installed with mounting.

Of course, this assumes this is a standard roof. Some can be weaker depending on the type of structure you’re installing panels on. Roof materials also play a role since materials like concrete tiles might need additional mounting and others like rubber or reflective materials may lower the efficiency of the solar panels.

How much space you have on your roof is also a major consideration. Solar panels are light enough to rest on roofs without any damage. That said, not every section of your roof may be facing the correct direction or allow for the right angle to make use of solar technologies.

This also relates to the size of solar panels, both in terms of capacity and their physical dimensions.

If you are installing 12 solar panels (350W), they would require a surface area of 24m². It is therefore important to know how much space you have. The table below outlines the average solar panel dimensions and weight per system size.

When deciding how many solar panels you need, it can be difficult to account for all the factors involved. This is why it’s best to consult a reliable installer and have them provide you with an estimate. Finding a reliable installer can take days of difficult research and calling up companies. If that sounds like too much hassle, why not try out our handy hassle-free service?

We can easily provide you with up to 4 free non-binding solar panel quotes in the UK and all you have to do is fill out a 30-second form. Click the button below to get started.

The average off-grid home will require a 7kW to 10kW solar panel system. Why so much compared to the modest 4kW system required for on-grid homes? Off-grid power has a lot more considerations.

Going off-grid usually requires a high-power system since you will often be compensating not just for electricity but also for gas. Therefore, the calculations are drastically different already. Added to this, you also need to compensate for the seasonal dips in energy generation during the winter.

These systems will cost between £12,000 - £13,000 and require between 38m2 to 54m2 of roof space, with more power needed since off-grid homes will need extra power. Similarly, off-grid living also requires a solar battery which may cost upwards of £8,000 on top of the solar panel costs if you want to use energy at night.