Solar Battery Storage Sizing Calculator
Estimate nominal battery storage needed for a selected daily energy use and autonomy period, after allowing for usable depth of discharge and system efficiency.
How to use this calculator
- Enter daily energy use, autonomy days, usable discharge percentage, system efficiency and nominal battery-bank voltage.
- Check the labels and units before applying the result to a real task.
- Change one input at a time when comparing scenarios.
Formula and method
Nominal storage = daily energy × autonomy days ÷ (usable DoD fraction × efficiency fraction)
- Nominal storage = daily energy × autonomy days ÷ (usable DoD fraction × efficiency fraction)
- This energy-sizing estimate does not check inverter surge, battery chemistry, cold-weather performance, ageing, electrical protection or local code requirements.
Worked examples
Worked example
Use 10 kWh per day for two days, with 80% usable depth of discharge and 90% efficiency.
Nominal storage ≈ 10×2/(0.8×0.9) = 27.78 kWh.
Nominal storage ≈ 10×2/(0.8×0.9) = 27.78 kWh.
Understanding the result
Estimate nominal battery storage needed for a selected daily energy use and autonomy period, after allowing for usable depth of discharge and system efficiency.
This energy-sizing estimate does not check inverter surge, battery chemistry, cold-weather performance, ageing, electrical protection or local code requirements.
Important notes
This energy-sizing estimate does not check inverter surge, battery chemistry, cold-weather performance, ageing, electrical protection or local code requirements.
Displayed values are rounded for readability; retain appropriate precision when continuing a calculation.
Frequently asked questions
Why is nominal storage higher than daily use?
The battery may not be intended to discharge to zero, and conversion losses mean stored energy exceeds the energy that must reach loads.
What does autonomy mean?
Autonomy is the number of days the planned load should be supported without the expected energy replenishment assumed by your system design.
Does this calculate solar panel output?
No. It estimates storage capacity. Panel output depends on location, season, orientation, shading, weather and other system factors.
Related calculators
- Solar Panel Sizing Calculator — Estimate a solar array size and panel count from daily energy demand, peak-sun-hours, system efficiency, and panel rating.
- Audio File Size Calculator — Estimate encoded audio file size from duration and average bitrate for podcast, music and storage planning.
- Video Bitrate and File Size Calculator — Estimate video file size from duration, video and audio bitrates and an overhead allowance.
- IPv4 Subnet Calculator — Calculate an IPv4 network address, subnet mask, broadcast address, and common host range from a CIDR prefix.
- Image Pixel Density Calculator — Estimate pixels per inch from image dimensions and a physical diagonal measurement.
- Sample Size Calculator — Estimate a simple random-sample size for a proportion using a chosen confidence z-score, assumed proportion and margin of error.
Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
- How to Calculate Salary from an Hourly Rate — Convert hourly pay into weekly, monthly, and annual estimates and understand the assumptions behind the result.
- How to Calculate Age from a Date of Birth — Learn how exact age is calculated using years, months, and days rather than a rough year difference.
- Percent Difference — Understand percent difference, when it is appropriate, and how it differs from percentage change and percent error.
This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.