How Many Batteries Do I Need For Solar?

An important thing to consider when installing a solar panel system is whether or not you want to add batteries for energy storage capabilities. There are many benefits that come with owning a battery, such as avoiding peak electricity costs, minimizing your carbon footprint, and having access to electricity during an outage.

On top of this, you are still likely to qualify for the 30% federal tax credit when you include a battery with your solar panel system. All of these features make batteries a great option for any solar panel owner.

Once you decide on having a battery, the next question is, “How many batteries do I need?”

Well, home solar batteries come in different sizes, so it may be more appropriate to figure out what capacity, power, and other specifications you need and then go from there. You should account for factors like your daily energy consumption, the specifications of your battery, and what the primary purpose of your home battery will be.

In most cases, people use their batteries to store excess energy for use at night or times when their panels are not generating any electricity. Therefore, most solar panel owners will only need enough stored power for one evening of use.

In this post, we will go over all of the details so that you can equip your solar panel system with the perfect home battery.

More About Home Batteries

To figure out what type and how many batteries you need, you must first understand some details about home batteries themselves. There are 3 main factors that will influence the solar panel owner’s decision about a home battery:

Capacity

The capacity is the total amount of electricity that the battery can store. This is measured in kilowatt hours (kWh) and represents how big the battery is. For example, Tesla Powerwall 2 has a 13.2 kWh capacity. Check this video to know more about kilowatt hours. 

Power Rating

The power rating for a solar battery is the amount of electricity that can be delivered at once. This is measured in kilowatts (kW) and directly impacts that quantity of electricity that can be drawn from the battery. So, if you want a battery that can power many of your household appliances and devices at once, you will need a high power rating.

Depth of Discharge (DoD)

The DoD is simply the amount of charge that was used by a battery. For example, if the battery has a 30% charge left, then the DoD is 70%. The reason why the DoD is important is that due to the chemical composition of some home batteries, you must ensure the DoD never gets to 100%. This means that for most home batteries, you will need the capacity to be slightly larger than the maximum amount actually needed.

Enough Batteries For The Evening

Now that we have the details, we can begin to look at the main use case for home batteries.

For the average home solar panel system, a battery serves as a backup for the evening and late night when the sun is down. To get an idea of how many batteries you need, all you need to do is figure out how much energy you use within this time-frame and find a battery that can deliver that quantity of kW to your home.

If the average monthly electricity consumption by a US household is around 900 kWh, then the amount of electricity that a household uses in one day is around 30 kWh. If we narrow this further to just the evenings, this is likely anywhere between 5-10 kWh that is being used.

What this means is that to meet the typical energy needs for this time frame, you will need a battery that is around 10 kWh in capacity with a power rating of at least 5 kW.

Batteries can be found in sizes ranging from under 2 kWh up to 16 kWh or more. They can even be connected together for a doubling of capacity.

Home battery power ratings can vary widely from battery to battery, and there are even incentives for some batteries that total in the thousands of dollars.

Several Home Battery Options

There are several home battery options available, and the capacity and power rating, among other factors, will all influence the number of batteries you will need, which may range from one to five batteries.

Some of our favorite batteries, however, include Tesla’s Powerwall and Sonnen, the LG Chem Resu 10H, and even a Mercedes-Benz home battery.

All of these options are suitable for the typical solar customer, so don’t hesitate in starting your search! Learn more about our home battery service here.