Interactive tool
CPAP Battery Runtime Calculator
Pick your machine, humidifier setting, connection, and battery to estimate how long it will run — and the minimum capacity you need for a full night.
Humidifier
Connection
Battery
Estimated runtime (DC cable, 18 W)
10.3–12.8 hours
✓ Covers your 8h night with ~2.3 hr to spare
Minimum capacity for 8 hours at this draw: 200 Wh
Batteries that cover this
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How this is calculated
Runtime = battery capacity (Wh) ÷ power draw (W) × an efficiency factor (0.85–0.90 for a DC cable, 0.70–0.80 for an AC inverter), with a 15% safety buffer applied to the conservative end for battery age and cold weather.
These are estimates. Your machine's actual draw varies with pressure, mask leak, altitude, and battery age and temperature. Check the label on your power supply, and don't rely on this tool for medical decisions.