What Size Solar Battery Do I Need UK?


Jack Ayre

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In order to optimise the power generated by your solar panel system, you may want to consider purchasing a solar battery. The device works by storing the excess electricity generated by your solar panels for you to use at a different time. If your generated electricity is coming up short on cloudy days or at night time, a solar battery is the perfect solution.

However, it can be difficult to determine what size solar battery you will require. If you purchase a battery too small, you may become more reliant on the grid. But if you select a battery too big, you will end up spending too much money and will not see a return on investment.

To help you better understand the complicated world of solar batteries, we have created this guide to help you work out what size solar battery you will need in the UK.

Why do I need a solar battery?

As the world tries to find new ways to promote environmentally friendly methods of generating electricity, the installation of solar panels has become increasingly more popular. However, the UK isn’t exactly known for being one of the sunniest places in the world. This can be seen in the table below which displays the average daily sun hours in the UK (with figures from the National Statistics publication Energy Trends produced by the Department for Energy Security & Net Zero.

Calendar period (2023)Average daily sun hours in the UK (provisional)


In order to maximise the use of solar energy, finding ways to efficiently produce, store, and use this electricity has become incredibly important. Which is where solar batteries come in.

By implementing a solar battery in your solar panel system, you will be able to utilise electricity produced through your solar panels outside of typical generating hours. With most individuals either working or out of the house during generating hours (when the sun is more likely to be shining), you will be missing out on hours’ worth of energy if you do not own a solar battery.

If you want to find out more about how a solar battery will benefit you, contact ESE Solar today!

Choosing the right solar battery size in the UK: Off-grid

For those living off-grid, calculating the size of solar battery you will require is quite complex. What you need to do is accurately estimate your total electricity consumption. You can do this by identifying the wattage requirements of the appliances and devices you wish to use powering your generated solar energy. Typically, you will be able to find the wattage requirements labelled on the device. 

The following method will tell you the number of watts you will require from your generator:

  1. If your device’s requirements are listed in either volts or amps, use the following equation  to find out the appliances running watts. Volts (V) x Amps (A) = Watts (W).
  2. Add together the running watts of all your devices, ensuring the number does not exceed the running watts listed on your generator.
  3. You will also want to factor in the starting watt requirement. You can do this by identifying the device with the highest starting wattage and add that number to the running wattage total so far.
  4. The number you now have is the total starting watts required for your generator, you must ensure that it does not exceed the starting watts rating of your generator.


However, if you are planning to use a device in a mobile off-grid setting then you may require the measurement power in amp-hours (Ah) and milli-amp hours (mAH). You can calculate your total consumption using Ah or mAH, and then you will need to convert amp hours to kilowatt hours (kWh). You can do this by multiplying the solar panel battery voltage by amps and divide it by 1,000.

Relating these measurements to solar batteries, you should select a solar battery size that is at least twice your daily usage.

Choosing the right solar battery size in the UK: On-grid?

If you currently live on-grid and have no intention of moving off-grid, then installing a solar battery is not essential for your solar panel system. This is simply because when your solar panels aren’t generating enough electricity to sustain your household requirement, your balance system will switch over to utility power.

However, there are various outside factors that may lead you to consider purchasing a solar battery. Taking into consideration the increasing demand on electricity, the energy crisis, extreme weather conditions, and the ageing infrastructure of the grid, you may benefit from purchasing a solar battery. The device will ensure you are not as reliant on the grid and it may save you a significant amount of money in the long run. Additionally, you may also be able to sell any excess energy produced back to the grid.

If you are considering purchasing a solar battery while still on-grid, at a minimum you should select a battery that can store the electricity you over-generate on a daily basis.

How important is it to get the right size solar battery?

Understanding the size of the solar battery you require before purchasing is very important. If you purchase a battery too small, then it will not provide the electricity you require to power your household. On the other hand, if you purchase a battery too big, then you will be spending an unnecessary amount of money and won’t see a return on investment.

Another consideration you should take into account is the amount of usable capacity a battery has compared to its total capacity. Also known as the depth of discharge (DoD), the typical amount of usable capacity is around 90 or 95% for modern solar batteries. Additionally, you may also wish to consider the power output, as batteries with a large capacity but low power output, may struggle to power your home.

solar battery

What size solar battery do you need for your home?

While every home will have varying energy requirements, the table below will give you a general outline of the solar battery size that you may require.

Property sizeBattery size in kWh
One bedroom2
Two bedroom4
Three bedroom8
Four bedroom9.5


Things to consider before purchasing a solar battery:

  • Do you have a smart metre? If you are struggling to calculate your power usage but you have a smart metre, the device will tell you the precise amount that you are using.
  • How powerful are your solar panels? Before purchasing a solar battery, you also need to consider whether your solar panel system is able to charge the battery throughout the day. If not, then the benefits of your solar battery will be minimised.
  • Take note of your battery’s cycle allowance: The battery’s cycles relate to the amount of times it can be charged and discharged. Typically, the larger the number of cycles the more you will get out of the battery before degradation starts. Additionally, your battery’s warranty could be linked to the amount of cycles it has. Alternatively, your solar battery warranty may be time-specific.


What size solar battery do I need FAQs:

How long does a solar battery last?

Well-maintained lithium-ion solar batteries can last up to 15 years. Whereas a lead acid solar battery may need to be replaced every 5-7 years.

Can I charge an electric car using a solar battery?

While you are able to charge an electric car using a solar battery, it may not be able to complete the job. The typical capacity of an electric car is approximately 40 kWh, meaning you may need either multiple solar batteries or one with a very large capacity to complete a full charge.

You may find it more efficient to use your solar panel system directly to charge your electric vehicle, and use your solar battery for other purposes.

How much money will I save with a solar battery? 

There is no set blanket amount that you will save by purchasing a solar battery. Additionally, the amount of money you may save as a result of using a solar battery can vary every month or year. However, an average three-bedroom household could save up to £783 a year through its solar panel system. 

In conclusion, what size solar battery do I need in the UK?

The solar battery size that you require will depend on a variety of different considerations. Do you live on-grid or off-grid? How big is your house? And what electricity requirements does your household have?

If you are opting to purchase a solar battery, ensuring that you have the correct size will open up a host of new benefits to you. From energy cost savings and doing your bit for the environment to having a more reliable energy source during this time of uncertainty. If you currently have a solar panel system in place without a solar battery, you may be missing out on hours of generated electricity by not having a storage solution.

To ensure that you get the right size solar battery for your household, get in touch with ESE Solar and start optimising your solar panel system today!

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Born in North West England, Jack kicked off his career in the insurance arena, dealing with claims for three years. Always up for a challenge, Jack leapt out of his comfort zone and embarked upon 5 years of excitement with the military.

Working for the Ministry of Defence, Jack specialised in counter-terrorism which took him to places such as Dubai, Oman, Iraq, Norway and Bahrain. During this period he worked with various Governments implementing strategic operations to prevent terrorism.

After travelling around various countries Jack increasingly came across various forms of solar from large solar farms to domestic solar panels. From here Jack took a keen interest in all things solar and started reading about the technological capabilities with a view to entering the industry after his career in the Ministry of Defence.

Once home after 5 fruitful years, Jack had 3 months leave in which he immersed himself in a solar crash course and got applying for jobs within the solar sector. He came across ESE Solar, a long-established forward-thinking company whose head office was only a stone’s throw away from him. He picked up the phone to see if there were any vacancies and within a week had a successful interview and obtained a full-time job, starting in the technical team.

Within the first few months, Jack onboarded in various online courses during work and social hours to speed up his knowledge of all things solar. Due to his strong work ethic and thirst for knowledge Jack was promoted to Head of Technical at ESE Solar. He currently leads the team and oversees the product development of new technologies within the company alongside assisting where necessary on their maintenance department.

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