You can buy a solar storage battery for less than £2,000 or more than £11,000. But if you're looking for a battery with a medium capacity of 5 kWh (kilowatt hours), which is ideal for a three-bedroom house, expect to pay around £5,000. Capacity is the main factor that dictates how much a storage battery costs. It works out at. Size isn't everything. The price of a solar storage battery is affected by many factors other than capacity. Brand name, for example – as you'll know if. The bigger your house and the more energy you use, the higher capacity your solar battery will need – and the more you'll need to pay for it. Here's a quick cost calculator to help you plan: By now, you've made up your mind whether or not to include a solar battery with your solar PV system. If you don't already have panels, the next step is to compare quotes for panels. A storage battery cuts your energy bills, shrinks your carbon footprint and can even keep your home running in a power cut. But it costs thousands to buy and install, and may not break even.