How to Use the CPAP Runtime Calculator
Enter your battery's watt-hour capacity, choose whether your CPAP's heated humidifier is typically on or off (which fills in a typical wattage), and set your usual hours of sleep per night — the calculator estimates total runtime hours and how many nights of backup that provides.
This tool is built specifically around the nightly-use pattern of CPAP therapy, rather than a generic one-time runtime estimate.
Choosing the right humidifier setting to model
As covered in the humidifier guide, selecting "off" gives you the maximum possible nights of backup, while "on" reflects your normal comfort setting — try both to see the real trade-off between comfort and available nights of backup power.
Treating the result as a planning estimate, not a guarantee
As covered in the how-to-power-a-CPAP guide, test your exact equipment combination in advance if you depend on CPAP therapy nightly — this calculator is a planning tool, not a substitute for that real-world test or for guidance from your medical equipment provider.