How Many Batteries Do I Need For Solar Panels?

So you’ve made the decision to go solar and you want to add batteries for storing energy. There is no question that there are benefits that come with owning batteries such as cutting down on peak electricity costs and not being restricted to access during outages. But just how many batteries do you need? 

Prior to purchasing a battery, you’ll want to take some time to understand the three main factors about solar panel batteries for homes: 

1. Capacity

Capacity is the amount of electricity a batter can store for future use. This electricity is measured in what is called “kilowatt hours” (kWh) and gives owners an idea of how big the battery is. 

2. Power Rating

Power rating refers to the amount of electricity that can be delivered at once. This is measured in kilowatts (kW). The power rating directly affects how much electricity that can be drained from the battery. For example, if you plan to run a lot of household devices at once, you’ll need a high power rating versus operating on a few select devices. 

3. Depth of Discharge (DoD)

While this term sounds complicated, the depth of discharge is simply the amount of charge used by a battery. This just tells you how much you have used of your battery’s percentage. For example, if the battery has 20% charge remaining, the DoD is 80%. Due to the chemical composition of some brands of batteries, the DoD should never get to 100%. Always look for a battery that will have a capacity slightly larger than what you require. 

Purpose

The actual number of batteries you’ll require will depend on the above three factors as well as your needs. On a typical basis, solar panel owners use a battery as a backup for the evening when there is no sunlight available. According to the U.S. Energy Information Administration, the average U.S. Household uses 867 kWh per month, which means approximately 29 kWh per day. So for estimation purposes, we can assume approximately 6 to 12 kWh being used at night. This can be covered by the use of a single 16 wKh battery or could be covered with several connected 2 wKh batteries. Batteries come in various sizes and can be combined together to store and provide more power as needed. 

To find out the number of batteries you’ll need for your solar panel is going to require some steady research and number crunching. There are lots of online calculators that can help depending on your needs. For example, you can find an off-grid calculator or look at this handy table of appliance electrical consumption.