Core concept
Rated capacity is the nominal battery size.
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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.
Planning impact
Usable capacity is what remains after losses and reserve.
What to verify
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.
Evidence and review
These sources support the definitions and planning method. Calculator results are still estimates, not measurements or guarantees.
- DOE Explains...BatteriesU.S. Department of Energy · Government reference — Open source
- SUN Inverter technical specificationsVictron Energy · Technical manual — Open source
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
Battery capacity (Wh): 1024 WhContinuous output rating (W): 1800 WSurge output rating (W): 2700 W
Estimated runtime13h 3m8h 10m – 16h 13mEstimated runtime: 13h 3m, 8h 10m – 16h 13m
Output path
Estimated runtime
13h 3mEstimated runtime: 13h 3mThis setup has comfortable headroom for overnight use, assuming the wattage estimate is realistic.
Conservative8h 10m
Estimated13h 3m
Optimistic16h 13m
Conservative assumes harder conditions; optimistic assumes favorable conditions.
- This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
- Usable energy
- 783 Wh
- Average load
- 60 W
- Fixed station overhead
- Unknown (not included)
- Running watts
- 60 W
- Max surge
- n/a
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
- Battery capacity (Wh): 1024 Wh
- Usable energy
- 783 Wh
- 1024 Wh x 85% x 90% x 100% x 100%
- Average load
- 60 W
- 60 W running, 60 W average after duty cycle and quantity
- Fixed station overhead
- Unknown (not included)
- 60 W / 85% = 70.6 W battery draw; fixed overhead is unknown and excluded
- Estimated runtime
- 13h 3m
- 783 Wh / 60 W = 13h 3m
- 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
- Fixed station overhead unknown; not included
This link contains the numeric values you entered, but not custom load names.
Source-Backed Next Steps
Smallest matching record (8h)Jackery Explorer 600 v2
WattRunTime.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
Fixed station overheadUnknown (not included)
Running watts60 W
Max surgen/a
Runtime range
Conservative8h 10m
Estimated13h 3m
Optimistic16h 13m
Show your work
Rated Wh is reduced by efficiency, reserve, battery health, and temperature before it is divided by average load.
Rated battery1024 WhBattery capacity (Wh): 1024 Wh
Usable energy783 Wh1024 Wh x 85% x 90% x 100% x 100%
Average load60 W60 W running, 60 W average after duty cycle and quantity
Fixed station overheadUnknown (not included)60 W / 85% = 70.6 W battery draw; fixed overhead is unknown and excluded
Estimated runtime13h 3m783 Wh / 60 W = 13h 3m
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
- 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.
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Use With These Tools
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Measured Runtime and Capacity Library
Compare calculated estimates with attributed delivered-energy tests.
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.