Battery Storage Calculator
Size a battery bank from daily energy use and days of autonomy, allowing for depth of discharge and round-trip efficiency. Gives kWh and amp-hours. Calculates in your browser.
Nominal capacity
-
Show the math
Size the bank so the usable energy still covers your autonomy after losses:
nominal kWh = (daily × days) ÷ (DoD × efficiency)
Ah = nominal Wh ÷ voltage
Depth of discharge protects battery life, lithium banks tolerate 80–90%, lead-acid usually 50%. All math runs in your browser.
What this does
A battery storage calculator sizes a battery bank from daily energy use and days of autonomy, allowing for depth of discharge and round-trip efficiency.
How to use it
- Enter daily energy use in kWh.
- Set the days of autonomy.
- Enter depth of discharge and efficiency.
- Read the kWh and amp-hours needed.
How it works
Usable capacity is less than nameplate — lithium tolerates 80–90% depth of discharge, lead-acid about 50%. Deeper cycling shortens battery life.
capacity = daily kWh × days ÷ (DoD × efficiency)
Understanding your result
Usable capacity is well below the nameplate figure, because you only safely use part of a battery: lithium tolerates 80 to 90 percent depth of discharge, lead-acid about half. Deeper, more frequent cycling shortens life, so a bank sized with honest autonomy days and a sensible discharge limit lasts far longer than one run to the bone every night.
Example
Backing 10 kWh/day for 2 days at 80% DoD needs roughly a 28 kWh bank.
Sources & methodology
Last updated .
Frequently asked questions
How big a battery do I need?
Multiply daily kWh by your days of autonomy, then divide by depth of discharge and efficiency to get the nominal capacity to install.
What is depth of discharge?
The share of a battery you can safely use \u2014 lithium tolerates 80\u201390%, lead-acid usually 50%. Deeper cycling shortens battery life.
Is my data stored?
No. Everything is calculated locally in your browser.
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