We recommend getting two or more batteries for your system. This allows you to use the energy from your solar panels when it’s most abundant. For example, if you have an energy-intensive appliance you want to use more often, such as a water heater, you can use the energy from the solar panels during the day when it’s most productive. If you go a year without using solar energy you will have to use your backup batteries which will be less efficient than your solar batteries.