According to the sleep foundation, there are more than 8 million CPAP users in the United States, and their essential machines need to be hooked up to a continuous supply of power. This is because virtually all CPAPs rely on plug-in electricity versus their own internal batteries. Nearly all devices on the market run off 120-volt outlets, and machines that come with a humidifier may use as much as 90 watts. During a power outage, some of which may last for days in severe weather, your machine’s internal battery will not receive a charge.