Calculator
Battery bank size for your daily load
Size the battery bank (Ah) needed to cover a daily energy use for a chosen number of backup days, accounting for usable depth of discharge, round-trip efficiency and temperature.
Related calculators
How many days your battery bank lasts
Usable capacity after depth-of-discharge
Series / parallel wiring configuration
Looking for a definition or a quick answer? See the solar & battery glossary for terms used on this page, or the FAQ for common sizing questions.
Sources & standards
- IEEE 1013 — Recommended Practice for Sizing Lead-Acid Batteries for Stand-Alone Photovoltaic Systems — Widely used engineering practice for days-of-autonomy and depth-of-discharge sizing methods, referenced here for the general sizing approach.
- UL 1973 — Batteries for Use in Stationary and Motive Auxiliary Power Applications — Safety standard most LiFePO4 and other stationary/portable battery packs are certified to.
- IEC 60896 — Stationary Lead-Acid Batteries (test & performance requirements) — International test standard covering VRLA (AGM/gel) and flooded stationary lead-acid batteries.
Estimates for planning only. Verify with a meter and follow NEC / local code; have a licensed installer confirm any system before purchase or wiring. See the methodology for formulas and sources.