Rated capacity is the nominal battery size
Rated capacity is the nominal battery size.
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.
Usable capacity is what remains after losses and reserve
Usable capacity is what remains after losses and reserve.
Measured capacity records are stronger than calculator estimates when the source is clear
Measured capacity records are stronger than calculator estimates when the source is clear.
Usable Wh = nominal Wh x efficiency x (1 - reserve) x battery health x temperature factor.
Usable Capacity vs Rated Capacity
A 1,000 Wh label is the starting point, not a promise that 1,000 Wh reaches your device.
Rated Wh Is The Label
Portable power stations and solar generators usually advertise nominal battery watt-hours. That number is useful for comparison, but it is measured before delivery losses and user reserve.
Usable Wh Is The Planning Number
The calculator reduces nominal Wh by the output path efficiency, reserve kept unused, battery health, and temperature loss before dividing by the load.
Measured Data Beats Guessing
When a third-party source publishes delivered Wh for the same model and output path, use that record as a reality check and keep unknown test conditions visible.
Try The Assumption
Open the calculator and change efficiency, reserve, health, or temperature to see why two stations with the same Wh label can plan differently.
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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 runtime13h 3m
Output path
Estimated runtime
13h 3mThis setup has comfortable headroom for overnight use, assuming the wattage estimate is realistic.
Usable energy783 Wh
Average load60 W
Running watts60 W
Max surgen/a
Conservative8h 10m
Estimated13h 3m
Optimistic16h 13m
Conservative assumes harder conditions; optimistic assumes favorable conditions.
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 60 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
Smallest matching record (8h)Jackery Explorer 600 v2WattRunTime.com
WattRunTime estimate
Estimated runtime
13h 3mThis setup has comfortable headroom for overnight use, assuming the wattage estimate is realistic.Usable energy783 Wh
Average load60 W
Running watts60 W
Max surgen/a
Runtime range
Conservative8h 10m
Estimated13h 3m
Optimistic16h 13m
Assumptions
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 60 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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Measured Runtime and Capacity Library
Open the calculator and change efficiency, reserve, health, or temperature to see why two stations with the same Wh label can plan differently.
Efficiency guide
Inverter Efficiency Losses
AC is convenient, but the inverter changes battery energy into wall-style power and some energy is lost as heat.
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 why rated watt-hours are not the same as usable watt-hours after inverter losses, reserve, battery health, and temperature.
Is usable capacity always lower than rated capacity?
For real device output, yes. Reserve, conversion losses, battery health, cold weather, and device behavior reduce the energy available to the load.
Should I replace the calculator estimate with measured Wh?
Use measured Wh when it matches the model and output path. If the load, temperature, or test conditions are unknown, keep the result as a planning estimate.