WattRunTime.com
Language

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.

Core concept

Duty cycle is the share of time a load is effectively running.

Planning impact

A refrigerator can have high running watts but lower average watts.

What to verify

Room temperature, door openings, settings, and insulation change the cycle.

Average load W = running watts x duty cycle.

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.

Evidence and review

These sources support the definitions and planning method. Calculator results are still estimates, not measurements or guarantees.

WattRunTime publishes source-based editorial calculations. We do not claim to have laboratory-tested these products or to provide medical or certified engineering review. Sources support specific statements; automated checks validate structure and arithmetic, not product truth. Third-party measurements name their publisher.

Editorial source review
Primary sources
2

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.

Loading calculatorPreparing calculator
Power station model
Battery capacity (Wh): 1024 WhContinuous output rating (W): 1800 WSurge output rating (W): 2700 W
EcoFlow DELTA 2
Estimated runtime4h 45m2h 58m – 5h 54mEstimated runtime: 4h 45m, 2h 58m – 5h 54m
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

Exceeds a tracked power limit — do not rely on these hours

This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior. Runtime is conditional on successful startup, compatible voltage/connectors and sufficient output. Verify the actual device setup before relying on these hours.

4h 45mEstimated runtime: 4h 45m

Exceeds a tracked power limit — do not rely on these hours

Conservative2h 58m
Estimated4h 45m
Optimistic5h 54m

These are calculated sensitivity cases, not a statistical confidence interval. Conservative uses lower efficiency and battery health, more reserve/temperature loss and higher load; optimistic changes these assumptions in the opposite direction.

  • This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior. Runtime is conditional on successful startup, compatible voltage/connectors and sufficient output. Verify the actual device setup before relying on these hours.
  • Exceeds a tracked power limit — do not rely on these hours
  • The largest startup surge (2900 W) is above the selected station surge rating (2700 W).

Show your work

Rated Wh is reduced by efficiency, reserve, battery health, and temperature before it is divided by average load.

Rated battery
1024 Wh
Usable energy
783 Wh
1024 Wh x 85% x 90% x 100% x 100%
Running watts
500 W
Average load
165 W
500 W running, 165 W average after duty cycle and quantity
Max surge
2900 W
Fixed station overhead
Unknown (not included)
165 W / 85% = 194.1 W battery draw; fixed overhead is unknown and excluded
Estimated runtime
4h 45m
783 Wh / 165 W = 4h 45m
Output path
AC inverter
Efficiency (%)
85
Reserve kept unused (%)
10
Battery health (%)
100
Cold weather loss (%)
0

This link contains the numeric values you entered, but not custom load names.

Source-Backed Next Steps

WattRunTime.com

WattRunTime estimate

Estimated runtime

4h 45mExceeds a tracked power limit — do not rely on these hours
Usable energy783 Wh
Average load165 W
Fixed station overheadUnknown (not included)
Running watts500 W
Max surge2900 W

Runtime range

Conservative2h 58m
Estimated4h 45m
Optimistic5h 54m

Show your work

Rated Wh is reduced by efficiency, reserve, battery health, and temperature before it is divided by average load.

Usable energy783 Wh1024 Wh x 85% x 90% x 100% x 100%
Average load165 W500 W running, 165 W average after duty cycle and quantity
Fixed station overheadUnknown (not included)165 W / 85% = 194.1 W battery draw; fixed overhead is unknown and excluded
Estimated runtime4h 45m783 Wh / 165 W = 4h 45m

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
  • Fixed station overhead unknown; not included

Warnings

  • This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior. Runtime is conditional on successful startup, compatible voltage/connectors and sufficient output. Verify the actual device setup before relying on these hours.
  • Exceeds a tracked power limit — do not rely on these hours
  • The largest startup surge (2900 W) is above the selected station surge rating (2700 W).

Use With These Tools

Related Guides

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.