Estimate portable power station runtime by dividing energy delivered to the load by its average demand. This guide uses nominal capacity and an explicit usable-energy assumption; it is not a manufacturer performance prediction.
Correction — October 22, 2026: Earlier versions included unsupported first-hand testing or experience claims. Those claims have been removed. This guide does not report measurements made by Wild Smart Gear.
The calculation
Estimated hours = nominal battery Wh × assumed usable fraction ÷ average load W. If you already know measured delivered Wh, use that directly and do not apply an additional usable fraction. For cycling loads, use a representative average or measured energy, not a peak rating.
Worked planning examples
| Nominal capacity | Assumed usable fraction | Average load | Calculated runtime |
|---|---|---|---|
| 500Wh | 80% | 50W | 8 hours |
| 1000Wh | 80% | 50W | 16 hours |
| 1000Wh | 80% | 100W | 8 hours |
All values are hypothetical inputs. The 80% fraction is an illustration, not a verified efficiency for a product. Replace it with evidence for your own output and load, and budget a reserve separately.
Where the estimate can fail
An AC output may have idle overhead, a low-load timeout or a load-specific efficiency. A compressor can cycle differently with temperature, and startup demand may exceed the output limit. Other devices sharing the battery and charging during use also change the budget. No default percentage validates every arrangement.
Example without a guarantee
At hypothetical 800Wh delivered energy and 50W average demand, runtime is 16 hours. At 100W it is 8 hours. These are arithmetic examples, not measured results for any product. Reserve, temperature and product limits still need consideration.
Device-specific planning
Use the 12V fridge guide for cycling cooler loads and the router runtime guide for network equipment. For CPAP, use the device-specific capacity guide and manufacturer instructions; this general formula does not establish medical equipment suitability.