How Does Solar Battery Storage Work?

 

Solar panels generate electricity whenever daylight conditions allow.

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Your home uses the electricity it needs first.

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If your solar panels are producing more electricity than the property is using, the surplus can be directed into a battery.

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The stored electricity can then be used later, perhaps during the evening when the family is home, appliances are running and the solar panels are producing little or no electricity.

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Once the battery has reached its minimum charge level, the property simply returns to drawing electricity from the grid in the normal way.

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Battery storage therefore allows you to shift solar electricity from the time it is generated to the time you actually need it.

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Can You Have Battery Storage Without Solar Panels?

 

Yes.

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A home battery does not necessarily need solar panels.

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A battery can also be charged from the electricity grid, particularly when used with a smart time of use tariff.

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Electricity can potentially be purchased during cheaper periods, stored in the battery and then used when grid electricity is more expensive.

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This can be particularly interesting for homes with higher electricity consumption, heat pumps, electric heating or other equipment that places greater demand on the electricity supply.

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The Energy Saving Trust confirms that battery storage can be used either with solar panels, with a smart time of use tariff, or with both.

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Make More Use of Your Solar Electricity

 

Without a battery, surplus solar electricity that your home cannot use immediately will normally be exported.

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That electricity may still have value through an appropriate export tariff, but the amount you receive for exporting electricity may be different from the amount you would otherwise pay to buy electricity back from the grid later.

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Battery storage gives you another option.

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Instead of immediately exporting all of the surplus, some electricity can be retained for your own use.

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This can increase what is sometimes called solar self consumption, meaning a greater proportion of the electricity generated by your roof is actually used within your own home.

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Can You Still Sell Electricity Back to the Grid?

 

Yes.

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Battery storage does not prevent a solar installation from exporting surplus electricity.

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Once your battery is sufficiently charged and your home does not need the additional solar generation, surplus electricity can still be exported.

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Eligible solar installations can receive payments for electricity exported through the Smart Export Guarantee. Electricity suppliers determine their own payment rates and contract terms, so it is worth comparing tariffs rather than assuming they are all the same.

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Some modern energy tariffs can also interact intelligently with battery systems, allowing electricity to be stored, used or exported at different times.

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This is one of the reasons battery storage should be considered as part of the home's wider energy strategy rather than simply as an accessory attached to solar panels.

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How Much Does Home Battery Storage Cost?

 

Battery prices vary considerably according to storage capacity, manufacturer, inverter requirements, installation complexity and whether the battery is being fitted alongside new solar panels or added to an existing system.

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Current Energy Saving Trust guidance suggests battery systems can range from around £1,500 to £10,000, with a typical 5 kWh battery system costing around £4,600.

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Larger homes and properties with greater electricity demand may require more storage.

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Some systems are also modular, allowing additional battery capacity to be added later.

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That does not mean that the biggest battery is automatically the best battery.

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The correct size should relate to the amount of electricity your home uses, when you use it, how much solar electricity you are likely to generate and what you want the battery to achieve.

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Home Battery Installations Currently Qualify for Zero VAT

 

There is also a useful financial incentive currently available.

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Installed electrical storage batteries in UK residential properties currently qualify for zero VAT until 31 March 2027.

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This applies both to batteries installed alongside qualifying technologies such as solar panels and to qualifying standalone battery installations connected to the electricity grid.

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That can make the current cost of installing battery storage considerably more attractive than simply looking at the headline equipment price.

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As with any tax relief, the installer should confirm the VAT treatment that applies to the proposed installation.

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How Large a Battery Does Your Home Need?

 

Battery capacity is normally measured in kilowatt hours.

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The Energy Saving Trust notes that a typical household battery system may be around 10 kWh, although there is no single capacity that is correct for every property.

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The important question is not simply:

How large a battery can I afford?

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It is:

How much storage can my home realistically use?

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A smaller household with modest electricity consumption may gain little from installing a very large battery.

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A larger household with solar panels, electric cooking, a heat pump, air conditioning and an electric vehicle may have completely different requirements.

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Future plans matter too.

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If you expect to install a heat pump or electric vehicle in the next few years, that additional electricity demand should be considered before selecting a battery.

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Solar Panels and Batteries Work Best as a System

 

Solar panels and battery storage are closely connected, but they should not be considered in isolation.

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A good system needs the right relationship between:

• The size of the solar array

• Expected annual solar generation

• Battery capacity

• Household electricity consumption

• Daytime and evening electricity demand

• Electricity tariffs

• Export payments

• Future heat pump installation

• Electric vehicle charging

• Available installation space

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Simply covering the roof with panels and installing the largest available battery does not guarantee the best financial result.

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The system needs to suit the property and the people living in it.

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Will a Battery Keep the Lights on During a Power Cut?

 

Potentially, but this should never be assumed.

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Some battery systems can provide backup electricity during a power cut when designed and installed with the necessary equipment.

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Other systems will not automatically continue powering the home when the electricity grid fails.

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If backup power is important to you, this needs to be discussed with the installer at the design stage.

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You should also decide which circuits actually need backup.

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Keeping lighting, communications, refrigeration and essential equipment operating may require a very different system from trying to power an entire house during an outage.

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How Long Does a Home Battery Last?

 

Battery life varies according to the technology, the manufacturer, the number of charging cycles and how the battery is used.

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Current Energy Saving Trust guidance suggests a typical home storage battery may last around 10 to 12 years.

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This means the battery may need replacing during the life of a solar panel installation.

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When comparing systems, homeowners should therefore look carefully at:

• Battery warranty

• Guaranteed usable capacity

• Expected cycle life

• Performance guarantees

• Replacement costs

• Manufacturer support

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The cheapest initial quotation is not necessarily the cheapest system to own over the longer term.

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Is Solar Battery Storage Worth It?

 

For some homes, absolutely.

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For others, the financial case may be less convincing.

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Battery storage tends to become more interesting when there is substantial solar generation that cannot be used during the day, higher electricity consumption during the evening, access to attractive smart tariffs or significant future electricity demand.

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But batteries are not free energy.

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There are costs involved, batteries gradually degrade and some energy is lost during charging and discharging.

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The Energy Saving Trust specifically advises that although savings can be significant, they will not always be sufficient on their own to justify the cost of the battery.

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That is exactly why the decision should be based on the individual property rather than on a sales quotation.

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Battery Storage and Heat Pumps

 

Battery storage can become particularly interesting when a home also uses a heat pump.

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Heat pumps transfer a significant part of the home's heating demand onto the electricity supply.

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A battery combined with an appropriate electricity tariff can potentially allow some electricity to be purchased or stored at more favourable times and then used when demand increases.

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Solar panels, batteries and heat pumps can therefore complement one another particularly well.

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However, the size and operation of the system need to be considered carefully.

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Adding expensive technologies without considering how they interact can result in a home that contains plenty of impressive equipment without necessarily delivering the best value.

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Battery Storage and Electric Vehicles

 

An electric vehicle can dramatically change a household's electricity consumption.

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If you already own an electric vehicle, or expect to buy one, its charging requirements should form part of any solar and battery assessment.

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The timing of charging can be just as important as the amount of electricity required.

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A smart charger, suitable electricity tariff, solar panels and home battery can potentially work together to make much better use of lower cost and renewable electricity.

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This is another reason to plan future energy requirements before choosing the size of a solar or battery system.

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Could Funding Help With Battery Storage?

 

Possibly.

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Government support for household energy improvements is evolving and some schemes may include battery storage for qualifying properties.

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The government has also confirmed that installed home electrical battery storage currently benefits from zero VAT until 31 March 2027.

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Funding availability depends upon the household, property, location and scheme in operation at the time.

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Before committing to an installation, it is therefore sensible to check the latest grants and funding opportunities.

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Do Not Start With the Battery

 

Start with the home.

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How much electricity do you use?

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When do you use it?

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How much solar electricity could your roof realistically generate?

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Could insulation reduce your energy requirement first?

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Are you planning a heat pump?

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Will you need electric vehicle charging?

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Would a smart tariff change the economics?

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Could you benefit more from spending some of the available budget elsewhere?

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Only once those questions have been considered can you properly decide whether battery storage should be part of your Green Home Plan.

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Find Out Whether Battery Storage Makes Sense for Your Home

 

An APN Green Homes Assessment looks at the property as a complete energy system rather than simply recommending individual products.

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We can consider solar panels and battery storage alongside insulation, glazing, heating, cooling, ventilation, heat pumps, electric vehicle charging and other improvements.

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The aim is to help you understand what is appropriate, what should come first and where your budget is likely to make the biggest difference.

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Every home is different. Your green home plan should be too.

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Before spending thousands of pounds on solar panels and battery storage, find out what combination of improvements makes sense for your property.

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Green Home Assessment — £495 + VAT

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Tip: Before you spend thousands improving your home, find out where your money will make the biggest difference.