Fan Runtime Planning
Estimate fan runtime at the speed you use, with separate treatment of energy, motor startup, and AC inverter overhead.
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Speed settings matter
Measure watts at the fan speed you expect to use. Do not assume consumption scales linearly with the control setting. For intermittent use, enter only active hours within the plan.
Some motors have a startup demand above running power. Enter manufacturer-documented magnitude and duration, or mark startup unknown. The capacity result alone cannot confirm that the station will start the fan.
AC fans also incur the selected conversion loss and inverter idle draw. A purpose-built compatible DC fan may follow a different route and connection constraints.
Match hours to the way the fan runs
For a fan left on continuously, enter the full operating period. If you measured average watts over a schedule that already includes pauses, use the entire measurement period and do not reduce the result again with a duty fraction. If you instead know on-state watts and a separate on/off schedule, use operating-watts mode with that duty fraction.
Oscillation, speed settings, and other enabled features should match the measurement. If the fan includes a heater or other high-power function, do not use the fan-only reading to represent that mode.
Choose the question you need answered
Use the example below and the main calculator to size capacity for a planned number of hours. Use the battery runtime calculator when you already know a station’s capacity and want a sustained-load estimate. In either case, continuous output, startup, and the physical connection remain separate requirements.
For a rechargeable USB fan, decide whether you are estimating operation, charging its internal battery, or both. Measure the actual session and avoid adding the same charging energy twice.
Worked illustration
An illustrative eight-hour fan plan
Suppose a fan averages 35 W at the speed you plan to use, for eight hours. Startup remains unknown, and a different speed needs its own measurement.
- Energy delivered to the devices
- 280 Wh
- Estimated nominal battery capacity required
- 410 Wh
Assumptions: full starting charge, 10% stopping reserve, 100% capacity factor, 85% AC efficiency, and 90% USB/DC efficiency. AC idle draw is 5 W for 8 hours when an AC load is present. Values are rounded for display.
Operating and startup power are intentionally unestablished in this energy illustration. Check those requirements and the actual connections before choosing equipment.
Build your own plan
The tool starts empty. Add the exact equipment you intend to use, choose the route it will connect through, and replace illustrative values with your measurements. Review Advanced settings before treating the result as a shopping requirement.
Step 2 · Check the requirements
Results
Your plan summary will appear here.
- Add each device and its time in this plan.
- Review the editable assumptions.
- Choose Calculate requirements.
No personalized result is shown until then.
Device
Related reading
Published by Portable Power Calculator. This is specification-based planning information, not a hands-on product test or electrical safety assurance.