Battery Backup Time Calculator
Accurately compute realistic backup hours considering Depth of Discharge (DoD), inverter conversion loss, and Peukert de-rating.
| Battery Option | Chemistry | Usable Wh | Expected Runtime |
|---|---|---|---|
| 100 Ah Tall Tubular (12V) | Tall Tubular Lead-Acid | 671 Wh | 2h 14m |
| 150 Ah Tall Tubular (12V - Most Popular) | Tall Tubular Lead-Acid | 1017 Wh | 3h 23m |
| 200 Ah Tall Tubular (12V) | Tall Tubular Lead-Acid | 1371 Wh | 4h 34m |
| 220 Ah Jumbo Tubular (12V) | Tall Tubular Lead-Acid | 1508 Wh | 5h 2m |
| 100 Ah Lithium LiFePO4 (12.8V) | Lithium LiFePO4 | 925 Wh | 3h 5m |
| 150 Ah 24V Dual Tubular (24V) | Tall Tubular Lead-Acid | 2035 Wh | 6h 47m |
Frequently Asked Questions
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Continue with another electricity or backup-planning tool.
Reference official efficiency and safety guidance from Bureau of Energy Efficiency and standards information from Bureau of Indian Standards.
Calculation Assumptions & Safety
Calculations are planning estimates using the displayed inputs and assumptions, not certified designs or verified provider bills. Actual runtime, generation, cost and wire requirements vary with equipment, installation and operating conditions. Confirm manufacturer specifications and current provider rules. Have a qualified electrician review wiring and backup installations.
Calculate backup hours from battery Ah and load
A 12 V, 150 Ah battery stores a nominal 1,800 Wh. At 50% usable discharge and 85% conversion efficiency, about 765 Wh reaches the load; at 150 W, illustrative runtime is 5.1 hours. Actual discharge performance varies.
How the calculation works
Hours ≈ V × Ah × usable discharge fraction × efficiency ÷ running watts, with any battery-rate derating applied where appropriate.
Compare household scenarios
- 100 W load: about 7.65 h under example assumptions
- 150 W load: about 5.1 h
- 250 W load: about 3.06 h
Common questions
- How long will a 150 Ah battery last?
- Runtime depends on battery voltage, chemistry, usable depth of discharge, inverter losses and the actual connected watts. Amp-hours alone are insufficient.