Battery storage allows you to keep electricity stored and ready so that you can use it when you need it. You can charge the batteries using excess electricity generated from solar panels or other home generation. Or you can charge them using your mains electricity supply. Energy storage can be useful if you generate renewable electricity and want to use more of it, or outside of daylight hours. It may also be worth considering if you have a time-of-use energy tariff that means you could charge a battery cheaply at off-peak times.

Solar panels with a solar battery

When you don't use all the energy generated by your solar panels during the day, a solar battery can store the excess so you can use it at another time. For example, at night or on particularly cloudy days when your panels aren't generating as much energy. This means you can use even more of your renewable and free electricity and buy less from your supplier.

While solar batteries can maximize your energy savings and lower your carbon footprint even further, many people assume that a solar battery will also be able to provide you with back-up energy during a power cut. While there are some solar battery systems which do have this feature, it is far more common that a solar battery cannot help you in a power cut.

Solar batteries and power cuts…what usually happens?

The reason why solar batteries often won't provide your home with back-up power is due to the safety risks involved in doing so. Your solar panels and battery are connected to the main grid. During a power cut engineers will be working on the grid and if solar panels or batteries are in operation there is a risk the engineers could be electrocuted by the electricity being generated. This is why solar inverters are designed to automatically switch off when a power cut is detected.

However, if your solar battery has back-up functionality, you will be able to use your solar energy during a power cut…

Solar batteries with back-up power…how do they work?

Solar batteries with back-up power have a relay (a switch) which will automatically disconnect your electricity supply from the grid when it detects a power cut. This is called islanding. This relay is installed between your main fuse board and the incoming electricity supply. You'll have power for your home so you can continue to use your electronic appliances, appliances and any electric heating during the power cut.

Some systems provide an almost seamless transition from grid power to solar back-up power so you may not even notice that there has been a power cut. This feature is called UPS (Uninterruptible Power Supply).

Will your solar panels continue to charge the battery during a power cut?

This depends on the type of back-up system you have. Some lower cost batteries will automatically discharge their stored energy when a power cut is detected. This is in part due to the fact that the battery inverter is usually smaller than the solar inverter; allowing the energy in the solar inverter to flow into the battery could overload it. However, if the battery inverter is larger than the solar inverter, energy can continue to flow into the battery until it is fully charged.

How much electricity can a back-up solar battery provide?

This depends on the size of the inverter in the battery. In a solar battery back-up system, the battery needs to hold enough power for your everyday use while keeping some energy in reserve in case a power cut happens. The larger the capacity of the battery in kW, the more energy you can reserve for power cut back-up and the more appliances you'll be able to run during a power cut.

It's important to work out how much electricity you want to store for daily use and how much you want to keep in reserve in case a power cut should happen. If you don't keep enough energy in reserve you won't have enough for a power cut, but if you keep too much in reserve you may find you don't have enough available energy to power your home on a standard day.

Moreover, in order to properly assess your specific needs and circumstances, it is highly recommended to get in contact with a professional in the field. Luckily, we are here to help by providing you with free and non-binding quotes.