Not all solar power systems need battery banks, but for an off-grid system, they’re essential to providing your home with continuous power, even when the sun goes down. When you don’t have the grid as a safety net to power your home, you need a backup power source of your own, and battery banks are the go-to. But how do you ensure your battery bank is large enough to meet your power needs? Keep reading to learn how to calculate the size of your bank.

Assess Your Energy Needs

Just as you have to do when sizing your solar power system, you’ll need to start out by assessing your energy needs. You should already have a good handle on this from your initial calculations, but as a quick reminder, here’s what you need to do: List all the electrical devices you intend to use, along with their wattage and the number of hours you use them each day. Multiply the wattage by the hours of use to get the daily watt-hour consumption for each device. Add these values to find your total daily energy requirement.

Determine Days of Use

You next need to determine the number of days that you want your battery bank to be able to provide your home with solar. Remember, this isn’t just the power you’ll use at night; this is also the power you’ll need during cloudy or rainy weather. Common practice is to plan for 3 to 5 days of use. Multiply this by the daily energy consumption you calculated above to get the total energy you need from your battery bank.

Account for Depth of Discharge

With batteries, it’s important to account for their maximum depth of discharge (DoD). Batteries cannot be completely discharged, or else you’ll significantly shorten their lifespan. This means you can’t look at the total storage capacity of the battery alone. If it has only a 50% DoD, it can only provide you with half of its stored energy. This is why it’s important to look for batteries with a DoD, known as deep-cycle batteries.

With all of these numbers in front of you, you should now be able to calculate the correct size for your battery bank on your Schneider off-grid solar system. Remember to err on the side of oversizing your battery bank, so that you don’t find yourself without power after a few days of cloudy weather.