How many hours a 700Wh station lasts on a 50W CPAP

A 700Wh portable power station can run a CPAP drawing a steady 50W for about 11–13 hours through its AC outlet. The simple calculation gives 14 hours, but the inverter and the CPAP’s actual power use reduce real-world runtime. If 50W is only the CPAP’s maximum rating, your runtime may be longer when its average draw is lower.

The runtime calculation

Divide the station’s energy capacity by the CPAP’s power draw:

700Wh ÷ 50W = 14 hours (theoretical maximum)

That assumes every watt-hour in the battery reaches the CPAP. When you use the station’s AC outlet, its inverter uses some energy converting battery power to household AC. As a planning estimate, allow roughly 10–20% for conversion losses:

• 700Wh × 0.80–0.90 = about 560–630Wh available to the CPAP
• 560–630Wh ÷ 50W = about 11–13 hours

The station’s own specifications may give a more precise usable-capacity or AC-runtime estimate. Actual results depend on the model, operating conditions, and load.

What can change your CPAP runtime

Humidifier and heated tubing

Heated humidification and heated tubing can raise power use, sometimes substantially. Their effect depends on the CPAP model and settings. If you need a reliable overnight estimate, use the device maker’s power guidance or measure its draw with an appropriate meter rather than assuming it stays at 50W.

Rated watts versus average watts

A label showing 50W may describe maximum or rated power, not the average draw during a night. If the CPAP averages less than 50W, it can run longer; if heaters push the load above 50W, it will run for fewer hours. The formula is usable watt-hours ÷ average watts.

AC versus a compatible DC connection

Using the AC outlet is convenient, but conversion losses reduce runtime. A manufacturer-approved DC power option may avoid some of those losses. Check the CPAP maker’s guidance for the correct cable, voltage, and connector; do not substitute a cable based only on a matching plug.

Is 700Wh enough for one night?

For an eight-hour night at a constant 50W, the CPAP would use about 400Wh before conversion losses. That makes a 700Wh station a reasonable capacity on paper for one night at that load, with some margin. The margin can shrink if the CPAP’s heaters increase its draw, the battery is not fully charged, or the station’s usable AC capacity is lower than its headline rating.

Before relying on the setup overnight, confirm that the station’s output and waveform meet the CPAP manufacturer’s requirements, and check the expected runtime with your actual settings. Follow the device and station manuals, especially if the CPAP is medically necessary. Do not change prescribed treatment settings just to extend battery life.