What happens if the power goes out at night and I am using AC power?
If you are using a portable oxygen concentrator then the device will switch automatically over to the Battery and you will have up to 8 hours (model dependent) of oxygen delivery if the battery is fully charged. If you are using a floor standing oxygen concentrator the device will cease to work and you will will want to swap to using backup oxygen if available.
AC power is provided when you plug a device into a mains plug. DC power is provided by batteries.