The size of a solar panel system is significant when determining the size of the battery you need as a battery's primary function is to store the excess energy produced by the solar panels especially when panels aren't producing as much power due to cloudy days.
However, it's not just about the energy generation capacity of your solar panels. You also need to consider your household's energy consumption. If your home uses a lot of energy, you might need a larger battery, even if your solar panel system isn't particularly large.
According to a study by the Renewable Energy Association (REA), the average size of a solar battery in the UK is around 4.8 kilowatt-hours (kWh).*
Again the size of the battery you need depends on your household's energy consumption and the output of your solar panels. Another factor to consider is the number of consecutive days your solar battery system can meet your energy needs without solar power input. If you want more days of autonomy, you'll need a larger battery, regardless of the size of your solar panel system. Larger batteries, such as those with a higher kilowatt-hour (kWh) capacity, offer the benefit of storing more energy.
Statistically, the average UK home uses around 8.5-10 kWh of electricity per day. Therefore, a battery of around 4-8 kWh would be sufficient for most households. However, if your solar panel system is larger or your energy consumption is higher, you may need a larger battery.
Batteries have a depth of discharge (DoD), which is the percentage of the battery's energy discharged relative to the overall capacity. Most batteries need to retain some charge at all times due to their chemical composition. Therefore, when considering the size of your battery, you need to account for its DoD. For example, if you need 10kWh of storage and your battery has a DoD of 90%, you'll actually need a battery around 11kWh in size.
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Larger Battery
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Smaller Battery
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| longer lifespan | more affordable |
| more expensive | requires less space |
| requires more space | more cost-effective option if your energy consumption is relatively low. |
| can lead to underutilization if your solar panels don't generate enough power to charge the battery fully, leading to inefficiencies. |
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The right battery size for your solar panel system depends on:
- your energy consumption,
- size of your solar panel system,
- your budget, and
- the amount of space you have available for battery storage.
Lastly, since you'll be paid for surplus energy exported back to the grid by the Smart Export Guarantee (SEG) you may not need as large a battery.
We liked this user friendly guide by Artisan Electrics. Work out your usage - the answers are all in the numbers.