What Is a Solar Battery and How Does Battery Storage Work?

Solar panels can generate a considerable amount of electricity during daylight hours, but the time when your panels are producing the most energy is not necessarily when your home is using the most. 

A solar battery helps solve this problem by storing electricity so it can be used later rather than immediately exported to the electricity grid.

For households looking to make greater use of their own renewable electricity, battery storage can therefore be an important addition to a solar PV system. But what exactly does a solar battery do and how does the process work?

What Is a Solar Battery?

A solar battery is an electrical storage battery that can store electricity generated by solar panels for later use.

During sunny periods, your solar panels may generate more electricity than your home currently requires. Without battery storage, this surplus electricity can be exported to the grid. With a suitable battery system installed, some of that excess generation can instead be stored.

The battery can then discharge when electricity demand increases or solar generation falls, such as during the evening or early morning.

Although commonly referred to as solar batteries, home storage batteries do not necessarily require solar panels. Many systems can also charge using electricity from the grid, allowing households on suitable time-of-use tariffs to charge their battery during cheaper periods and use that electricity later when grid prices are higher.

How Does Solar Battery Storage Work?

A typical solar PV and battery storage system continually monitors how much electricity the panels are generating and how much electricity the property is consuming.

During the daytime, electricity produced by the solar panels is normally used by appliances in the home first.

If your panels are generating more electricity than you are currently using, the remaining energy can be directed towards the battery. Once stored, that electricity remains available until it is required.

Later in the day, when your solar panels are producing less electricity, the battery can begin discharging to help meet the property's electrical demand.

If the battery reaches its minimum charge level, the home can return to drawing electricity from the grid as normal. Similarly, if the battery becomes fully charged while the panels continue producing excess electricity, the remaining surplus can normally be exported to the grid.

Much of this process happens automatically through the battery system, inverter and associated energy management controls.

Can a Solar Battery Charge From the Grid?

Yes. Modern home battery systems can often be configured to charge from the electricity grid as well as from solar panels.

This can be particularly useful alongside a time-of-use electricity tariff where electricity costs less during certain periods. A battery may be charged overnight or during another cheaper tariff window before supplying some of that stored electricity when rates increase.

As a result, battery storage can potentially be useful even for households without solar panels, although the financial benefit will depend heavily on electricity consumption, tariff rates and the cost of the system.

What Does Solar Battery Capacity Mean?

Solar battery capacity is normally measured in kilowatt-hours or kWh. This tells you approximately how much electrical energy the battery can store.

It is important not to confuse capacity in kWh with power output in kW.

Capacity describes how much energy can be stored, while power output affects how much electricity the battery can supply at a particular moment.

A larger battery is not automatically the best choice. The right capacity will depend on factors including household electricity consumption, the size of the solar PV system and when electricity is typically used.

If you are unsure how much storage would suit your household, our guide to what size solar battery you need explains how usage, solar generation and daily consumption affect battery sizing 

What Are the Benefits of Adding Battery Storage?

One of the main advantages of battery storage is the ability to use more of the electricity your solar panels generate yourself.

Instead of exporting surplus generation during the day and then buying electricity back from the grid later, stored solar energy can be used during periods when the panels are generating less.

Depending on the installation and electricity tariff, battery storage may also help households:

• Reduce the amount of electricity purchased from the grid

• Make greater use of their own solar generation

• Shift electricity consumption away from expensive tariff periods

• Monitor and manage household energy use more closely

• Store cheaper off-peak electricity for later use

Whether battery storage provides worthwhile savings will depend on the individual property, electricity consumption and tariff, so system sizing is particularly important.

If you are weighing up the financial side of battery storage, our guide to whether solar batteries are worth it in the UK looks at potential savings, tariffs and the factors that influence payback. 

Is a Solar Battery Right for Your Home?

A battery can make a solar installation considerably more flexible, but there is no single capacity or specification that suits every property.

Before choosing a system, consider how much electricity your household uses, when you use it, the output of any existing solar panels and whether you intend to charge the battery from the grid as well as from solar generation.

You can explore our range of solar batteries to compare available capacities and storage solutions for residential solar installations.

Understanding how battery storage works is the first step. The next question is whether the potential savings and additional solar energy you can use make a solar battery worthwhile for your particular home.