Traditional building-mounted fixtures on generators or AC power systems can be used for both normal and emergency egress lighting. An emergency generator provides continuous AC power to the fixtures on the emergency circuit(s) during loss of normal power. An AC power system utilizes batteries and converts DC to AC power for the fixtures on the emergency circuit(s) during loss of normal power.

When using incandescent or fluorescent lamps for emergency egress lighting, an emergency generator or interruptible AC power system can be used. If using HID lamps, a fast-transfer AC power system or uninteruptible power supply is required to switch the power quickly enough so that the HID lamp does not lose its arc and extinguish.