Should I Add Batteries to My Solar System? Also, How Many?

How much battery do you need

Ever since Tesla launched Powerwall in circa 2015, home batteries have taken off. Today, there are several battery providers who offer a range of sizes, functionality, and yes, awesome aesthetics. Check out this blog to see who they are and what’s popular today. 

No, we are not skirting the fundamental question. Do you even need batteries? A lot of Americans have said yes (battery sales have been growing exponentially in USA) and here’s why: 

1. Batteries Lower Electric Bills:  Batteries will savings to your electric bill — beyond what you would save with solar.  

Net Metering: Many utility companies will give you credit for the excess energy you produce from your solar panels and put back into the grid, which is called net metering. But other utility companies actually charge a fee for net metering or don’t give you any credit for back-fed energy. If you can store the excess energy in a battery system instead of sending it back to the grid, you’ll save more in the long run in these situations.  

Read More About: Solar Batteries Lifespan 

Control over Peak Charges: A solar battery system can increase your electric bill savings if your utility company charges different rates at different hours (which most do!). With battery, you can store excess energy during off-peak hours and use that energy during peak times to avoid paying higher rates.  

Demand Charges: Some utility providers charge based on the largest amount of power you draw at any one time (yup!). You can program a solar battery system to provide power when you have higher demand to reduce your bills. 

2. Independence: The key benefit of solar battery storage is energy independence. As power outages become more common, having backup power is critical. 

3. Tax Credits and Rebates: Batteries have the same 30% ITC tax rebate as solar. It’s just part of the deal. 

4. BONUS: Increase your home value: According to research by Zillow (the uber popular real-estate marketplace), you can increase your home value by 4% (or more) by installing solar with batteries. 

Plus, the usual (also most important IMO) – add batteries allows you to use more of the renewable energy you generate. You save the planet one KWh at a time. Also, batteries don’t make noise, they look cool, and you can have them put in the garage with your main panel. 

Read More About: How Many Solar Panels Do You Need? 


We will keep this really simple. You need two numbers to calculate. How much power you consume in a day and DoD. We will get to DoD in a minute.  

You can find out how much power you consume in a day from your electricity bill. It shows you how many KWh you consume in a month. Just divide that by 30. 

DoD is the term used to describe the percentage of a battery’s capacity that can be used before recharging is required. It is calculated by dividing the amount of energy taken out of the battery by its total capacity. Don’t worry, all battery vendors publish this number so all you have to do is look it up. 

So, to calculate the required battery size for your personal use, you can use the following super-simple formula: 

Battery Size (kWh) = Daily Energy Consumption / DoD 

Example: Let’s say your daily consumption is 10kWh and DoD is 80%. You should get batteries which are 10/80% or 12.5KWh.  

Want to learn more? Talk to a trusted, local installer who is a community partner and knows what works in your area (the local incentives, regulations, and codes etc). Click here to pair up!

  • by Understand Solar
  • |
  • March 26, 2024