UK Solar Battery Storage: The Complete Guide

If you’re looking to install a solar battery system, there are probably a few questions on your mind like:

How much do they cost, and how much can they save me on my electric bills?

• Battery systems are the ideal complement for solar panels. You can store electricity and use it at any time, even when there is no sunshine to power your panels.
• The cost of a home battery can range from £3,000 to more than £10,000, depending on its brand and energy storage capacity.
• Home batteries are exempt from the VAT when installed along with a solar panel system.
• Without a battery, any excess production from your solar panels must be sent to the grid. You are paid a reduced export tariff, not the full value of each kWh.
• A battery bank increases the savings achieved by your solar panels: excess production can be stored instead of being sent to the grid, and you save its full value.
• You can find home battery systems from many manufacturers in the UK, including: Tesla, LG, Enphase, Huawei, Powervault, Duracell, SolaX, Moixa, AlphaESS and Puredrive.

The price of solar panels has been decreasing in recent decades, and they can now generate electricity at a lower cost than fossil fuel power stations. However, solar panels have technical limitations like any other generation system:

• Photovoltaic (PV) cells can only produce electricity when the sun is shining, and they only reach peak production for a few hours around noon.
• As a result, solar panels cannot provide power “on demand” like a petrol generator.
• Solar panels by themselves cannot provide backup power during a blackout. Their electricity output is variable, and your home appliances need a stable power source.

The technical limitations of solar PV systems can be eliminated by adding a battery bank. You can store electricity when your solar panels are productive and use it later: at night, on cloudy days, during blackouts, etc. Stand-alone solar panels cannot operate 24/7, but a charged solar battery can be used regardless of sunshine conditions.

What’s in this guide?

Compare My Solar Prices

Get quotes from local installers

1 fast form = 4 low quotes

Save up to £703 per year

GET QUOTES NOW

Solar Battery Costs

Solar battery system costs between £2,000 for a small solar battery in the UK, and prices can exceed £10,000 if you want a system capable of powering your entire home.

These prices depend on its brand, chemical composition and energy storage capacity.

For example, the Tesla Powerwall is a popular solar battery with a storage capacity of 13.5 kilowatt-hours (kWh). The official price published by the Tesla UK website is £6,000, and the installed price can range from £9,000 to £13,000.

The payback period of a solar battery varies widely depending on your electric tariff and energy usage habits. However, there is also a non-financial reason to install a battery: having a backup power source that does not depend on fuel deliveries.

When Does a Solar Battery Make Sense?

In many cases, a home battery can increase the savings achieved by a solar panel system. Even if a battery does not increase your savings by a significant amount, it can be used as a backup power source during blackouts. Here are some general scenarios where installing a solar battery makes sense from a technical or financial standpoint:

When you are paid a low tariff for excess solar energy

If your solar PV system generates more electricity than what your home needs, the difference is sent to the National Grid. The Smart Export Guarantee (SEG) scheme ensures you are paid for this excess energy, but most electric companies offer low tariffs. As a result, the kilowatt-hours (kWh) sent to the grid are much less valuable than the kWh you use directly. 

Here is a simplified example:

• Assume your electricity provider charges 35 pence/kWh, but they only pay 6 pence/kWh when your solar panels have surplus production.
• If you have 10 kWh of excess production during a summer day, your compensation is only £0.60 (10 kWh x £0.06/kWh).
• On the other hand, if you store these 10 kWh in a solar battery and use them at night, you save the full value of £3.50 (10 kWh x £0.35/kWh).

If you consider a 30-day billing period with an excess production of 10 kWh/day, you get £18 for exporting 300 kWh to the grid. On the other hand, if you store 10 kWh/day in a battery and use them at night, you save £105 during the same billing period.

When you want to use solar power during blackouts

There is a common misconception that solar panels can keep your home powered during a blackout. However, this is only true if the system includes a battery bank. Stand-alone solar panels cannot be used as a backup power source:

• If you measure the output of a PV system in real time, you will notice that productivity is constantly changing along with sunshine conditions.
• For example, if the weather is sunny but a large cloud passes over your home, there is a notable drop in energy production.
• Since your home devices need a constant source of power, stand-alone solar panels cannot be used as a backup generator.

However, you can store electricity in a solar battery system, and use it as your backup power source. A battery system is optional if your only goal is saving on power bills, but it becomes mandatory if you want to use solar energy during blackouts.

When you want to go off-grid

You also need a battery system if you plan to go off-grid with solar energy. As explained above, solar panels by themselves cannot provide electricity 24/7. If you want an off-grid power source that is fully independent from the grid, you must add a large battery bank to your PV system.

An off-grid solar battery must be sized larger than a backup power battery, which means it also has a higher price:

• If you want to go completely off-grid, your solar battery must have enough capacity for cloudy days and other extended periods of low sunshine.
• On the other hand, if you only want a backup power source for blackouts, your battery only needs storage capacity for a few hours.

Going off-grid is a lifestyle decision, but you can achieve a better ROI with a grid-connected solar battery. An off-grid battery must be sized for the worst-case scenario, while a grid-tied battery can be sized for optimal savings. Using the grid occasionally as backup is more cost-effective than installing a 100% off-grid solar system and spending 2-3 times more.

Grants and Tax Exemptions

VAT Exemption

The UK offers a Value-Added Tax (VAT) exemption for solar panels, but keep in mind that this exemption only applies for complete systems installed by professionals. If you buy solar panels from a retailer with no installation services included, you are charged the VAT.

Home batteries are not directly covered by the VAT exemption. However, a battery installed along with solar panels is considered part of the same project, and eligible for 0% VAT. There are two important requirements:

• You must purchase the solar panels and battery from the same provider.
• Both systems must be installed at a single project: if you install the solar panels first and the battery at a later date, it does not get the VAT exemption.

Not paying the VAT represents major savings. For example, if you purchase a stand-alone battery for £9,000, the 20% VAT is £1,800. On the other hand, if you purchase this battery along with a 4-kW solar system having a price of £8,400, you save the following taxes:

• £1,800 for the battery purchase
• £1,680 for the solar panel system
• £3,480 in total

Considering how the VAT exemption works, it makes sense to install your solar panels and home battery as a single project. Also consider that UK electricity prices exceed 30 p/kWh: changing a battery with your own solar energy is much cheaper than using grid power.

The following table lists the battery incentive schemes that are currently active in the UK:

Note that smaller programs may be available locally from your council or utility company. The best solar companies are well informed about solar PV and battery incentives in all the regions where they operate.

Savings

As mentioned above, the savings achieved by a solar battery can vary widely depending on your energy usage habits and electric tariff. A home battery can increase the savings achieved by solar panels if you meet two conditions:

• You are exporting a large fraction of your solar electricity instead of using it directly.
• You are paid a low export tariff when sending excess solar energy to the grid.

This scenario can be explained more easily with an example. Assume you have a 5-kW solar system that generates 4,500 kWh/year, but you only use 900 kWh directly while exporting 3,600 kWh to the grid. Assume you are charged an electric tariff of 35 p/kWh, but only get 5 p/kWh when exporting excess energy.

• Direct savings = 900 kWh x £0.35/kWh = £315 per year
• Solar exports = 3,600 kWh x £0.05/kWh = £180 per year
• Total savings = £495 per year

According to the Department of Net Zero and Energy Security, home solar systems with a size of 4-10 kW have a mean price of £2,100/kW. This means you can expect to pay £10,500 for a 5-kW system. If you only save £495/year, the payback period is extended to 21.2 years.

If you could use the 4,500 kWh directly, you would be saving £1,575 per year. You can achieve this by storing your excess solar energy in a battery instead of sending it to the grid.

• If you invest an extra £9,000 in a home battery, the project cost increases to £19,500 but your savings are tripled.
• In this case, the payback period is reduced to 12.4 years.

NOTE: This is just a simplified example that shows the potential value of a solar battery system. To determine the actual savings you can achieve in your property, you need a professional energy assessment.

Compare My Solar Prices

Get quotes from local installers

1 fast form = 4 low quotes

Save up to £703 per year

GET QUOTES NOW

Best Brands

The Tesla Powerwall is one of the most popular home batteries, but there are many other brands who offer comparable quality and performance. Here is a list of some high-quality solar batteries you can find in the UK:

Home battery systems normally have a 10-year warranty period, but specific terms and conditions vary depending on the brand. For example, some manufacturers specify a maximum number of cycles, and the warranty ends if you reach this threshold in less than 10 years.

According to the Federation of Master Builders, residential lithium-ion batteries have a typical installed cost of £1,000 per kWh of capacity. This means you can expect to pay around £4,000 for a 4-kWh battery and £10,000 for a 10-kWh battery. Keep in mind that prices can vary depending on the brand and installation company.

If you want to get the VAT exemption, you must purchase your home battery along with a solar panel system. Otherwise, you pay an extra 20%.

Adding a Battery to a Solar Panel System

Solar panels and batteries both operate with DC power (direct current), while your home appliances use AC power (alternating current). This means you need an inverter to use electricity generated by solar modules or stored in a battery. There are two possible configurations:

• DC-Coupled System: Your solar panels and battery use the same inverter.
• AC-Coupled System: Your solar panels and battery use separate inverters.

To set up a DC-coupled solar battery, you need a hybrid inverter. This is a special type of inverter that is compatible with solar panels and battery systems operating simultaneously. Traditional inverters are designed exclusively for solar panels, and they cannot manage the charging cycle of a battery.

• DC-coupled solar batteries are often recommended for homeowners who have not installed solar panels.
• Instead of  purchasing a solar panel inverter and a battery inverter, you can use a single hybrid inverter.

An AC-coupled solar battery has its own inverter, which means your solar panels and battery can operate independently.

• This configuration is often recommended for homeowners who already own solar panels.
• There is no need to modify the existing installation, since you simply add a battery with a dedicated inverter.

DC-Coupled vs AC-Coupled Battery: Which Option is Better?

Like in any design decision, each option has pros and cons. The following table compares both solar battery configurations:

DC-coupled batteries charge more efficiently, since hybrid inverters can supply DC power directly from the solar array. On the other hand, an AC-coupled battery requires two power conversions when charging, since there are two inverters involved. This makes the charging process slightly less efficient.

Do I Need a Charge Controller to Use a Solar Battery?

A charge controller is a device that regulates the voltage and current supplied to a battery during its changing process. Charge controllers are necessary in off-grid solar systems, but not in grid-tied installations. The charge controller function is included in the hybrid inverters used for DC-coupled systems, and in the battery inverters used for AC-coupled systems.

Types of Batteries

Batteries can be classified based on their chemical composition. Most of the battery systems installed with solar panels can be classified into two main types:

• Lithium-ion batteries
• Lead-acid batteries

A battery stores and releases energy by exchanging electrical charge between two terminals called electrodes. This is accomplished by different materials depending on the type of battery, but the basic principle stays the same. 

Lithium-ion batteries can store electricity more efficiently than lead-acid batteries, and they have a longer service life. However, lead-acid batteries are more affordable. There are other types of batteries, but their technical requirements are too complex for residential usage.

Lithium-ion batteries

Lithium-ion batteries are the most common option for grid-tied solar energy systems. The latest Li-ion batteries have a service life of over 4,000 cycles, which is equivalent to more than 10 years with a daily charging cycle. These batteries can achieve a round-trip efficiency of over 95%, which means only a small amount of energy is lost in the charging cycle.

There are many subtypes of lithium-ion batteries, but two are the most common in solar energy applications:

• Lithium nickel manganese cobalt oxide (NMC)
• Lithium iron phosphate (LFP)

NMC batteries have a higher power density, which means they are lighter and more compact than LFP batteries of the same capacity. LFP batteries have a longer service life, but their typical cost is around 30-50% higher.

Lead-acid batteries

Lead-acid batteries are more affordable, and this is the type of battery used in traditional vehicles (non-electric). Lead-acid batteries have a much shorter service life than Li-ion batteries: they can last for around 1,000 cycles under optimal conditions, but their actual lifespan is closer to 500 cycles in real-world applications. These batteries are also less efficient than Li-ion batteries, with a typical round-trip efficiency of 70-80%. 

Lead-acid batteries are more common in off-grid solar systems, and they can also be used as a backup power source. However, these batteries have a very short service life if charged and discharged daily: a lead-acid battery rated for 500 cycles would only last 16-17 months under a daily workload.

Off-Grid

Using solar panels and batteries to go 100% off-grid is possible. However, this type of system is not financially viable for most homes. The best recommendation is using solar energy to reduce your power bills as much as possible, while staying connected to the grid.

UK electricity prices increased by 55% between 2022 and 2023, but having the grid as backup is useful in spite of its high tariffs. For example, when the weather is cloudy for several days in a row, your solar panels may not generate enough energy to cover your consumption.

• If you stay connected to the National Grid, your solar PV + battery system can be sized optimally for your typical consumption.
• If you go fully off-grid, your system must be upsized for the worst-case scenario.

You can install a solar power system with energy storage for less than £20,000. On the other hand, an off-grid solar system can cost upwards of £30,000, since it must be sized for unfavourable scenarios. The following are some examples:

• Days with above-average electricity consumption. For example, this can happen on a cold winter day if your home uses electric heating.
• Days with below-average solar productivity. For example, this can be caused by cloudy weather or winter days with reduced sunshine hours.

If you size a solar battery for these conditions, your project budget can increase by around £10,000 – £20,000. Even if electricity prices are high, using the grid occasionally is far less expensive than doubling the size of your solar battery.