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CPAP Runtime Calculator
CPAP runtime changes sharply when humidifiers and heated tubes are enabled, so this calculator keeps that assumption visible.
Quick answers by battery size
Server-rendered examples using this scenario's sourced planning default. Use the calculator for your exact station and settings.
Swipe table sideways
| Nominal capacity | Estimated runtime | Planning range | Static example |
|---|---|---|---|
| 300 Wh | 5h 44m | 3h 35m – 7h 8m | See Goal Zero Yeti 300 example |
| 500 Wh | 9h 34m | 5h 59m – 11h 53m | See Goal Zero Yeti 500 example |
| 1,000 Wh | 19h 8m | 11h 58m – 23h 45m | See Goal Zero Yeti 1000 LiFePO4 example |
| 2,000 Wh | 1d 14h | 23h 56m – 1d 23h | See Jackery Explorer 2000 v2 example |
| 3,000 Wh | 2d 9h | 1d 11h – 2d 23h | See Jackery Explorer 3000 Pro example |
These are calculated planning estimates, not measured runtimes. Actual results vary with load, battery condition, temperature, and output path.
Calculator
Start with a quick estimate, then switch to Advanced if you need multiple devices, startup surge, battery health, or cold-weather loss.
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Power station model
Battery capacity (Wh): 1024 WhContinuous output rating (W): 1800 WSurge output rating (W): 2700 W
Estimated runtime19h 35m12h 15m – 1d 0hEstimated runtime: 19h 35m, 12h 15m – 1d 0h
Device scenario
Output path
Humidifiers and heated tubes can more than double power draw. This is a comfort-focused estimate, not medical advice. Use the CPAP manufacturer's battery guidance for critical planning.
Estimated runtime
19h 35mEstimated runtime: 19h 35mThis setup has comfortable headroom for overnight use, assuming the wattage estimate is realistic.
Conservative12h 15m
Estimated19h 35m
Optimistic1d 0h
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
- 40 W
- Fixed station overhead
- Unknown (not included)
- Running watts
- 40 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
- 40 W
- 40 W running, 40 W average after duty cycle and quantity
- Fixed station overhead
- Unknown (not included)
- 40 W / 85% = 47.1 W battery draw; fixed overhead is unknown and excluded
- Estimated runtime
- 19h 35m
- 783 Wh / 40 W = 19h 35m
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 40 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)BLUETTI AC50B
WattRunTime.com
WattRunTime estimate
Estimated runtime
19h 35mThis setup has comfortable headroom for overnight use, assuming the wattage estimate is realistic.Usable energy783 Wh
Average load40 W
Fixed station overheadUnknown (not included)
Running watts40 W
Max surgen/a
Runtime range
Conservative12h 15m
Estimated19h 35m
Optimistic1d 0h
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 load40 W40 W running, 40 W average after duty cycle and quantity
Fixed station overheadUnknown (not included)40 W / 85% = 47.1 W battery draw; fixed overhead is unknown and excluded
Estimated runtime19h 35m783 Wh / 40 W = 19h 35m
Assumptions
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 40 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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Plan overnight CPAP power needs.
CPAP without heated humidifier worked example
A 1,024 Wh station with 10% reserve and 85% efficiency leaves about 783 Wh before load behavior. Using this page's 40 W default at 100% duty cycle, the planning load is about 40 W and the estimate is 19h 35m.
Change first
- Change watts first if your device label, meter reading, or power path differs from the default.
- Check startup surge for motors, compressors, and pumps.
- Use measured watts for outage or medical-adjacent planning.
CPAP without heated humidifier assumptions
Review the CPAP without heated humidifier scenario page when you need the wattage range, duty cycle, confidence label, and source notes before calculating runtime.
This calculator gives a planning estimate. Treat the result as a starting point, then refine it with measured watts, the device manual, and the station's current output limits.
Verify your watts
- Check the device label for running watts or input amps and volts.
- Use a plug-in watt meter for AC loads when the result matters.
- For cycling loads, measure long enough to capture on/off behavior.
Check output path
- AC inverter loads usually lose more energy than direct DC loads.
- Keep reserve for cold weather, battery age, and load changes.
- Do not treat label capacity as fully usable watt-hours.
Medical-device planning
- Use this site as a planning estimate, not medical advice.
- Follow the device manufacturer's battery guidance.
- Test the full setup before relying on it overnight.
Need a CPAP backup plan?
Use the CPAP Battery Backup Guide when humidifier settings, heated tubing, AC vs DC power paths, and nights of backup matter.
Related Guides
Use these explainers when an assumption changes the runtime result.
Efficiency guide
Inverter Efficiency Losses
Apply the guide to this use case's load and operating pattern.
Margin guide
Reserve and Battery Health
Apply the guide to this use case's load and operating pattern.
Related Calculators
Use the related tools when charging, sizing, surge, or power path changes the answer.
FAQ
These answers keep the estimate grounded in assumptions instead of pretending runtime is exact.
How many watt-hours does a CPAP need overnight?
A CPAP without heated humidification may use roughly 240 to 480 Wh over eight hours. Heated humidifiers and tubes can raise that substantially.
Can I use this for medical backup planning?
Use it only as a planning estimate. For medical devices, follow the manufacturer guidance and keep a tested backup plan.
Should I reserve 20% battery?
A 10% to 20% reserve is a practical buffer for uncertainty, startup spikes, and avoiding a completely empty station during an outage.
Why is real runtime lower than the label capacity?
Battery label capacity is nominal. Inverter losses, DC conversion losses, reserve settings, cold weather, battery age, and changing device loads all reduce real runtime.
How do you calculate portable power station runtime?
Use usable watt-hours divided by average load watts. For AC loads, a practical first-pass formula is battery Wh x efficiency x reserve factor divided by device watts.