Core concept
Wh describes stored or delivered energy; W describes the rate of using it.
Electrical units
Watt-Hours, Amp-Hours, and Voltage Explained
Watt-hours describe energy, amp-hours describe electric charge, and voltage connects the two. An Ah or mAh rating without its matching voltage is not enough for an energy comparison.
Planning impact
The same Ah rating represents different Wh at different voltages.
What to verify
Use the nominal voltage tied to the capacity label, not an unrelated output voltage.
Wh = V × Ah. Ah = Wh ÷ V. Wh = V × mAh ÷ 1,000.
Watt-Hours, Amp-Hours, and Voltage Explained
Watt-hours describe energy, amp-hours describe electric charge, and voltage connects the two. An Ah or mAh rating without its matching voltage is not enough for an energy comparison.
Power is not energy
Watts are an instantaneous rate. Watt-hours add time: a steady 100 W load for one hour uses 100 Wh. Amp-hours track charge rather than energy, so they cannot replace Wh by themselves.
Voltage completes the conversion
A 10 Ah rating at 12 V equals 120 Wh, while 10 Ah at 24 V equals 240 Wh. Use the battery or pack's nominal voltage associated with the Ah rating. Do not substitute a USB, AC, charger, or open-circuit voltage unless the manufacturer ties it to that capacity claim.
A capacity conversion is not a runtime result
After converting to Wh, runtime still depends on output-path efficiency, reserve, battery health, temperature, and the device's average load. If the source omits voltage, keep Wh unknown instead of guessing.
Evidence and review
These sources support the definitions and planning method. Calculator results are still estimates, not measurements or guarantees.
- Electric Vehicle Supply Equipment InfrastructureU.S. Department of Energy · Government reference — Open source
- NIST SI electrical and energy conversion factorsNational Institute of Standards and Technology · Government reference — Open source
Convert first, then estimate runtime
Use the matching nominal voltage in the capacity converter, then carry the resulting Wh into the runtime calculator with visible loss and reserve assumptions.
Loading calculatorPreparing calculator
This tool didn't load
Something blocked the calculator from starting. Check your connection or reload the page to try again.
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 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.
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.
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
Estimated runtime13h 3m783 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
- This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
This link contains the numeric values you entered, but not custom load names.
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
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
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
Warnings
- This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
Share URL
Use the right next step
Related guides
Portable Power Station Runtime Calculator
Apply this guide's assumptions in the runtime calculator.
Battery Runtime Calculator
Turn battery capacity and voltage into a usable-energy plan.
Battery Capacity Converter
Convert Wh, Ah, and mAh only with the matching voltage.
Watt Hours to Amp Hours Calculator
Convert Wh, Ah, and mAh only with the matching voltage.
Portable Power Station Size Calculator
Turn the required runtime into a capacity target with margin.
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.
Wh, Ah, and voltage FAQ
Understand Wh, Ah, mAh, volts, and watts before converting battery capacity or estimating runtime.
Which voltage should I use for Ah to Wh?
Use the nominal battery or pack voltage published with that Ah rating. If the documentation does not connect a voltage to the capacity, do not infer Wh from a different port rating.
Can I compare two power banks by mAh alone?
Not reliably. Compare Wh when both products publish it, or convert only when each mAh rating has a known corresponding nominal voltage.