Power Station Runtime Calculator
Estimate portable power-station runtime using capacity, conversion efficiency and appliance duty cycle.
Currency selection changes the unit label, not an exchange rate. Enter every price in the selected currency.
How to choose the inputs
Capacity is entered in Wh, not kWh. Enter the appliance power while running and the percentage of time it runs. Alternatively, enter measured average power and set duty cycle to 100%; do not reduce an average a second time.
Formula and measurement boundary
Three worked scenarios
These are fixed hypothetical examples, not live tariffs or verified product data. They use EUR and kilometres where applicable and do not change with the form settings. Only the table input changes.
Unchanged inputs
- Station capacity: 1,000 Wh
- Conversion efficiency: 85 %
- Appliance running load: 100 W
| Duty cycle | Estimated result |
|---|---|
| 25 % | 34 h 0 min |
| 50 % | 17 h 0 min |
| 100 % | 8 h 30 min |
The station supplies an assumed 850 Wh in these examples. The effective loads are 25, 50 and 100 W. A lower duty cycle extends the energy estimate, but it does not reduce the instantaneous power needed when the appliance starts.
What this result does not establish
- The calculation does not check the AC outlet rating or start-up surge.
- Fixed inverter idle draw is omitted; estimates can be optimistic for small loads.
- Use an efficiency appropriate to the output you actually use: AC, USB or DC.
Small loads make idle consumption especially important
The following are additional hypothetical decision examples. Separately discussed fees, reserve allowances or running costs are not automatically added to the form result.
For an illustrative 1,000 Wh station, first reducing the capacity input to 900 Wh for a 10% reserve and then applying 85% AC efficiency leaves 765 Wh. A 60 W laptop at 100% duty then gives 12.75 hours in a simple constant-load model. If the AC inverter also draws 10 W continuously and that demand is not already captured in the efficiency assumption, the effective load is 70 W and runtime falls to 10.93 hours. Do not add idle losses twice.
A laptop’s charger rating is a maximum, not its usual draw. Measure the workload you intend to run, including external screens. For a camping fridge, log a full warm-day cycle: compressor cycling and ambient conditions make a single instant reading unreliable. USB-C or DC operation may have different losses from AC; use an efficiency appropriate to the output actually used.
Before relying on the station, test the intended load from a known starting charge to the chosen reserve. Keep track of whether pass-through charging or auto-off settings change operation. The runtime estimate says nothing about output waveform, medical-device suitability or a motor’s starting surge. Capacity and watts must both fit the task.
Sources and their scope
- EIA: measuring electricity — Power and energy units only; not equipment performance.
These reference pages were accessed on 21 September 2026. The equations and examples are the site’s own model; these sources do not certify its defaults or results.
Frequently asked questions
How do I enter several devices?
Add their measured average watts and use a 100% duty cycle; check their combined peak power separately.
Does 1,000 Wh mean 1,000 W output?
No. Stored energy and maximum output power are separate ratings.
Read the model and verification limits