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How Many Solar Panels Do I Need to Power a Home in the UK?

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The number of solar panels you need to provide electricity for a home depends on three main factors:

  1. The amount of electricity you want to generate each year from solar panels, which is measured in kilowatt-hours (kWh).
  2. The solar resources available in your location. Sunshine rates tend to be higher near the equator and the tropics, and lower as you move farther north or south.
  3. The individual wattage of each solar panel. As the rated wattage increases, the number of panels needed to reach a specified system wattage is less.

In this article, we discuss the main factors that determine the number of solar panels needed for a UK home, followed by a simplified example. There are additional factors that come into play, such as roof pitch and local shading conditions. However, these are site-specific issues that are analysed by solar companies before installing a photovoltaic (PV) system.

How Much Energy Do You Want to Generate with Solar Panels?

To cover 100% of your home electricity consumption with solar panels, the output of your system must be equivalent to your annual electricity usage.

  • According to the Office of Gas and Electricity Markets (Ofgem), the average UK home uses 2,900 kilowatt-hours (kWh) per year.
  • This is also the electricity output that must be generated by solar panels to cover 100% of consumption in a typical UK home.

Ofgem also provides average consumption data for smaller and larger households:

Type of PropertyAnnual Electricity Usage in the UKHow Many Solar Panels You Need (240w each)
Flat or single-bedroom home, with 1-2 people1,800 kWh7-8
2-3 bedroom home with 2-3 people2,900 kWh12
4+ bedroom home with 4-5 people4,300 kWh18

Based on these figures and local sunshine rates, we can determine the number of solar panels that would be needed in each type of property. Solar installation companies use advanced simulation software to estimate electricity output by month, based on the solar radiation available throughout the year.

Does the UK Get Enough Sunshine for Solar Panels?

The British Isles are not a very sunny location, but local energy prices have been increasing rapidly in recent years. Between March 2022 and March 2023, the Department for Energy Security and Net Zero reported a 57% increase in domestic electricity prices.

  • As of 2023, UK residents are paying electric tariffs of over 30 pence/kWh.
  • For a household with the average consumption of 2,900 kWh/year, this results in annual electricity cost of over £900.

Considering the rising cost of electricity in the UK, solar panels offer an attractive return on investment even with modest sunshine.

You can easily visualise solar resources in any geographic location with the World Bank Global Solar Atlas. If you click on any location on the map, the Atlas display detailed information about local sunshine, but in this case we are interested in two specific values:

  • Specific Photovoltaic Power Output (PVOUT) = The annual electricity output per each kilowatt of solar panel capacity, assuming favourable site conditions.
  • Optimum Tilt of PV Modules (OPTA) = The tilt angle that maximises the electricity output of solar panels in a given location. The tilt angle assumes south-facing panels in northern hemisphere countries such as the UK, and north-facing panels in the southern hemisphere.

As you can see in the map, the PVOUT values in the British Isles range from around 1,100 kWh per kilowatt of peak solar capacity (kWp) in the south coast, to less than 900 kWh per kWp in northern Scotland. The optimum tilt angle for solar panels (OPTA) ranges from around 37° – 38° in the south to 41° – 42° in the north.

If you know the annual electricity consumption of your home and the local PVOUT value, you can estimate the solar capacity needed to cover your electricity needs.

What Solar PV System Size Do I Need for a UK Home?

To estimate the solar PV capacity needed for your house, you can divide annual consumption by the PVOUT value from the Global Solar Atlas. Just keep in mind that the value displayed on the Atlas shows an ideal scenario – even with favourable site conditions, the actual productivity of your solar panels may be around 10-20% below the ideal value.

As a quick example, assume you have a 3-bedroom house that uses 2,900 kWh per year, and the Atlas shows a PVOUT value of 1,000 kWh/kWp. If you can achieve 85% of this productivity, your solar panels would be generating 850 kWh per kilowatt of capacity per year.

  • Estimated solar system capacity = (2,900 kWh) / (850 kWh/kWp) = 3.4 kW

In this case, a 3.4-kW solar system would be capable of generating all the electricity needed by your home. As of 2023, you can find residential solar panels with a rated power output of over 400 watts. A solar power system with eight 400W panels would have a total capacity of 3.2 kW, enough to cover most of your annual consumption in this example.

Keep in mind this is a very simplified example, but it gives you an idea of the solar PV system size needed by a typical UK house. You can contact a solar company to get a site assessment and a customised offer, with an accurate calculation of your power bill savings.

Payback Period of Residential Solar Panels in the UK

Each month, the Department of Energy Security and Net Zero publishes cost data for solar PV systems in the residential sector. According to their most recent data (as of September 2023), homeowners who install solar panel systems with a size of 0-4 kW are paying an average price of £2,365 per kW.

  • Based on this price figure, the typical cost of a 3.2-kW home solar system is £7,568.

To estimate annual savings, we must consider that solar panels only generate electricity during the day, while homes consume energy day and night. To solve this, many governments have introduced net metering or solar buyback policies:

  • Your solar panel system can be designed to generate excess electricity during the day.
  • This surplus energy is exported to the grid and sold to local energy companies.
  • You get a power bill credit, which is subtracted from your consumption.

The UK previously had a mechanism called the feed-in tariff, which assumed your home was using 50% of its solar production and exporting the remaining 50%. In January 2020, the feed-in tariff was replaced with the Smart Export Guarantee (SEG), where you are paid for the exact amount of electricity sent to the grid.

Note that the SEG tariff for excess solar energy is normally smaller than the kWh price charged for your normal consumption. There are many SEG tariffs in the market, which range from 1 to 30 pence per kWh. However, the higher SEG tariffs tend to have complex requirements, and you will most likely get a solar export tariff in the range of 5-12 pence/kWh.

3.2-kW Home Solar System: Estimated Savings and Payback Period

With the solar resources available in the UK, a 3.2-kW solar panel system can generate around 2,720 kWh/year. The actual savings depend on your electric tariff, the SEG tariff you get for solar exports, and how your solar generation is split among self-consumption and grid export:

  • As a quick example, assume you pay 35 p/kWh for consumption, while getting 12 p/kWh for excess solar energy.
  • Assume your home uses 60% of the electricity generated by solar panels (1,632 kWh), while the remaining 40% goes to the National Grid (1,088 kWh).

Here is a calculation of the expected annual savings under this scenario:

    • Direct savings by using solar energy = 1,632 kWh x £0.35/kWh = £571.20
    • Income from solar exports = 1,088 kWh x £0.10/kWh = £108.80
  • Total savings = £571.20 + £108.80  = £680

If you paid £7,568 for the 3.2-kW solar energy system, the payback period is 11 years. This can seem like a long time, but the lifespan of high-quality solar panels is much longer. The leading solar panel brands are now offering 25-40 year warranty coverage, which means you get over 15 years free electricity after recovering your investment.

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Ollie Smith Photo

Ollie Smith

Ollie is the director of Ecopreneurist, with a string of successful publishing brands under his belt, he aims to make the world a better place by showcasing only the best, unbiased and reliable content on the web!

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