Because most customers cannot accept power at distribution voltage, it is usually lowered to the desired service voltage by a service transformer at or near the point of delivery. Connecting the service transformer to the customer circuits is the service, which includes the wires that run into the facility, the meter that measures electric deliveries, and the protective devices that ensure the safety of the service and circuits within.
Electrical services are provided in different configurations depending on the needs of the customer and the design of the customer’s distribution circuit. Common variables include the service voltage(s); overhead versus underground service; single-phase versus three-phase service; two-wire, three-wire, or four-wire service; and, in the case of three-phase service, wye versus delta.