Battery runtime calculator
How long will a battery run your devices? Enter its size in amp-hours or watt-hours, its voltage and type, and the load in watts. Example: a 100 Ah 12 V LiFePO4 battery runs a 100 W device on an inverter for about 8.2 h.
Your battery
Your load
Add up devices instead
1,200 Wh × 80% usable × 85% inverter ÷ 100 W = 8.2 h.
Same battery, common devices
| Device | Watts | Runtime |
|---|---|---|
| Laptop | 50 W | 16 h |
| Phone charging | 10 W | 3.4 days |
| Wi-Fi router | 15 W | 2.3 days |
| LED light bulb | 10 W | 3.4 days |
| Flat-screen TV | 120 W | 6.8 h |
| Refrigerator | 50 W avg | 16 h |
| CPAP (no humidifier) | 40 W | 20 h |
| Electric blanket | 85 W | 9.6 h |
| Fan | 65 W | 13 h |
| Desktop PC + monitor | 270 W | 3.0 h |
| Coffee maker | 1200 W | 41 min |
| Microwave | 1100 W | 45 min |
| Toaster | 1400 W | 35 min |
| Space heater | 1500 W | 33 min |
| Hair dryer | 1875 W | 26 min |
| Vacuum cleaner | 1440 W | 34 min |
Large AC loads also need an inverter rated for their watts; this calculator only answers how long the energy lasts.
How the battery runtime is calculated
- Energy: watt-hours = amp-hours × volts. A 100 Ah battery at 12 V holds 1,200 Wh.
- Usable share: you shouldn't drain a battery to zero. Victron Energy puts usable capacity at about 50% for lead-acid (AGM, gel) batteries in deep-cycle use and 80% (preferred) to 98% for LiFePO4. We default to 50% and 80%; change it if your battery's manual says otherwise.
- Inverter loss: for AC devices, about 85% of the energy reaches the plug (the planning factor Jackery publishes for its power stations). DC devices skip the inverter.
- Runtime: hours = Wh × usable share × efficiency ÷ load watts.
Real batteries can deliver less: lead-acid loses capacity at high loads and in the cold, and old batteries hold less than their label says. Treat the result as a planning estimate. More detail on our method page.
Questions
How long will a 100Ah battery last?
A 100 Ah 12 V battery holds 1,200 Wh. On a 100 W AC load it lasts about 8.2 h if it's LiFePO4 (80% usable) and about 5.1 h if it's lead-acid (50% usable). Halve the load and the runtime doubles.
How do I convert amp-hours to watt-hours?
Multiply by the voltage: 50 Ah × 12 V = 600 Wh; 100 Ah × 24 V = 2,400 Wh. Portable power stations are rated in Wh, so this is also how you compare a battery with a power station.
Why does a lead-acid battery give less runtime than a lithium one of the same Ah?
Draining lead-acid deeper than about half shortens its life sharply, so only about 50% counts as usable. LiFePO4 batteries can routinely use 80% or more of their rating.
How long will a power station run my devices?
A power station is a battery plus inverter in one box. Use the power station calculator to size one for several devices, or see the runtime guides for a single device on every popular model.