Tool
Runtime Estimator
Pick a capacity, pick what is running, and read the hours. The formula and the derate are printed beside the result rather than hidden inside it, so you can check the arithmetic and disagree with the assumptions.
Estimate
Rated capacity of the battery
What is running
There is no medical or life-sustaining equipment in this list, and there never will be. Powering that equipment is planned with the equipment supplier and with your electric utility, not estimated on a web page.
Sump Pump is also absent from this list. This site publishes no hour figure for that load at all, because the duty share the formula needs is not knowable in the conditions where the load matters, and a figure that cannot stand on its own page should not be quietly added into a total here.
How they run
Estimated runtime
Estimated from 1,024 Wh rated capacity carrying 3 loads drawing 57 W in total. This is an estimate, not a guarantee.
The formula on screen
hours = (rated Wh x 0.85) / (sum of average watts)
- Inverter and usable-capacity derate
- 0.85
- Usable watt-hours after derate
- 870 Wh
- Combined average draw
- 57 W
What this estimate does not account for
- Startup surge. A motor pulls several times its running current for a fraction of a second, and an inverter either supplies that or faults.
- Temperature. A pack in a cold garage gives back less than the same pack indoors.
- Battery age. Cells lose capacity with cycles, and a pack several years old is not the pack on the label.
- The efficiency of your specific model. One derate is applied to every unit here; real inverters differ.
- The real cycling of a refrigerator or freezer, which depends on the room, the contents, and how often the door opens.
- Your actual appliance. The wattages here are ranges; the nameplate on your own device is the figure that applies.
Every figure this tool produces is an estimate, not a guarantee. It does not promise that any unit will run any appliance for any length of time.
What the two modes mean
- All at once adds the average draw of everything selected and divides the usable watt-hours by that total. It is the pessimistic reading and the one that matches a household that plugs everything in and leaves it.
- One at a time splits the usable watt-hours evenly between the selected loads and adds up how long each runs on its share. It always produces a longer figure than the first mode, because nothing is competing for the inverter at the same moment.
- Neither mode says anything about whether a unit can start a motor. That is decided by the surge demand, not by the capacity, and it has its own reference page.
Where this tool stops
Hard limits on what this tool will estimate
- No medical or life-sustaining equipment appears in the load list and none ever will. That planning belongs with the equipment supplier and your electric utility, including asking about a medical registry and priority restoration before an outage.
- Nothing here describes connecting a power station to a wall outlet, a breaker panel, or house wiring. Powering house circuits from a portable source is a licensed electrician's job with a transfer switch.
- No figure here is a guarantee. It is an estimate produced by dividing derated watt-hours by a steady wattage, and it does not promise that any unit will run any appliance for any length of time.