Duty cycle is the share of time a load is effectively running
Duty cycle is the share of time a load is effectively running.
Load behavior guide
Duty Cycle Explained
Some devices do not draw their running watts all the time. Duty cycle is how the calculator turns cycling behavior into average load.
A refrigerator can have high running watts but lower average watts
A refrigerator can have high running watts but lower average watts.
Room temperature, door openings, settings, and insulation change the cycle
Room temperature, door openings, settings, and insulation change the cycle.
Average load W = running watts x duty cycle.
Duty Cycle Explained
Some devices do not draw their running watts all the time. Duty cycle is how the calculator turns cycling behavior into average load.
Average Watts Drive Runtime
Runtime math divides usable Wh by average load W. For cycling devices, the average can be far below the running watts printed on a label.
Fridges Are The Common Example
A compressor starts, runs, then rests. Warm rooms, frequent door openings, and poor insulation can increase the duty cycle and shorten runtime.
Measure When It Matters
For outage planning, a plug-in watt meter over several hours is stronger than a default. Keep startup surge separate from duty cycle.
Test A Cycling Load
Use the refrigerator preset, then change duty cycle in Advanced mode if your watt-meter reading or environment differs from the default.
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Power station model
Power station modelEcoFlow DELTA 2
Battery capacity (Wh): 1024 WhContinuous output rating (W): 1800 WSurge output rating (W): 2700 W
Estimated runtime4h 45m
Device scenario
Output path
Fridges cycle on and off. The calculator treats the entered wattage as compressor running wattage and applies a duty-cycle estimate.
Estimated runtime
4h 45mThis setup is tight. Reduce load, use DC where possible, or choose a larger station.
Usable energy783 Wh
Average load165 W
Running watts500 W
Max surgen/a
Conservative2h 58m
Estimated4h 45m
Optimistic5h 54m
Conservative assumes harder conditions; optimistic assumes favorable conditions.
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 165 W average load from 1 load
- 100% battery health
- 0% temperature loss
- This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
Source-Backed Next Steps
WattRunTime.com
WattRunTime estimate
Estimated runtime
4h 45mThis setup is tight. Reduce load, use DC where possible, or choose a larger station.Usable energy783 Wh
Average load165 W
Running watts500 W
Max surgen/a
Runtime range
Conservative2h 58m
Estimated4h 45m
Optimistic5h 54m
Assumptions
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 165 W average load from 1 load
- 100% battery health
- 0% temperature loss
Warnings
- This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
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Use With These Tools
Related Guides
Portable Power Station Runtime Calculator
Use the refrigerator preset, then change duty cycle in Advanced mode if your watt-meter reading or environment differs from the default.
Battery Runtime Calculator
Use the refrigerator preset, then change duty cycle in Advanced mode if your watt-meter reading or environment differs from the default.
Fridge Runtime Calculator
Use the refrigerator preset, then change duty cycle in Advanced mode if your watt-meter reading or environment differs from the default.
Emergency Backup Calculator
Use the refrigerator preset, then change duty cycle in Advanced mode if your watt-meter reading or environment differs from the default.
Appliance Wattage Library
Use the refrigerator preset, then change duty cycle in Advanced mode if your watt-meter reading or environment differs from the default.
Capacity guide
Usable Capacity vs Rated Capacity
A 1,000 Wh label is the starting point, not a promise that 1,000 Wh reaches your device.
Margin guide
Reserve and Battery Health
A runtime plan is safer when it leaves margin for age, cold, changing load, and measurement error.
FAQ
Learn how cycling loads such as refrigerators change average watts and portable power station runtime estimates.
Is duty cycle the same as startup surge?
No. Duty cycle affects average energy use over time. Startup surge is a short power spike that matters for whether the station can start the load.
Can I use 100% duty cycle?
Yes for steady loads such as many routers, lights, or electronics. Cycling appliances need a lower or measured value.