Single-phase is a service configuration offered by electric utilities and is typically provided to residential and small commercial customers. It is most often provided as 120/240V service, 120 volts for the lights and the outlets and 240 volts for the large energy-using appliances.

Single phase is more widely available in residential settings and is less expensive to purchase than three phase power units. Single phase is commonly called “residential voltage” for many reasons; one of which, is that most homes use it (it's the power present in wall plugs).