Example calculation
Solar Plan Lab uses the current project values to show how the recommendation changes.
Interactive planning tool
Solar battery sizing calculator
Convert essential load and desired backup duration into usable and nominal storage capacity.
No account Instant result Explanation included
1Tell us what you knowStart with the fields you already understand.
2See the recommendationSee the number and why Solar Plan Lab suggested it.
3Refine or downloadChange the plan before you buy or download anything.
New to solar? You do not need to choose a calculator first. Build a guided home solar plan →
Need help with watts? Not sure how many watts your essential appliances use? Use the Appliance Load Estimator first, then size storage from the appliances you actually want to keep running. Open Appliance Load Estimator →
1
Inputs
Enter what you know
Start with the simple fields. Open Advanced only when you need more control.
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Not sure what to enter? Keep the starting values you do not know yet and change only the values you can confirm. Every field now includes an i explanation and an example value.
Do not rely on one number alone
Check the result against actual equipment and site conditions.
Is this installation-ready?
No. It is a planning estimate that should be verified by qualified professionals.
How was this calculated?
Calculation method
Formula
The calculator uses the displayed inputs and standard planning relationships.
Important assumptions
Read the methodology → Verify the final design against actual equipment data sheets, site conditions, and applicable requirements.