Back To Basics

When dealing with an electrical distribution system, there needs to be some way to measure the power going into a residence or building. The utility company does not allow for unmetered power to be used. Consequently, every Service Entrance needs a separate meter for accurate billing of power consumption.

What is a Meter?

A meter is the device used to measure this power. The unit of measurement is the Watt/Hour. For this reason it is typically called a Watt/Hour Meter.

Figure 2. Typical Watt/Hour Meter

Components of a Residential Metering System

There are three main components to a watt/hour meter system. These are the Measuring Device, the Meter Socket and the Jaws.

The measuring device itself is typically supplied by the utility company.

It was once common practice for the local utility to also provide the meter socket, but that is no longer true for a growing number of geographical regions in the United States. In many cases, because of deregulation, providing the meter socket is now the job of the electrical contractor. The meter socket is the receptacle for the meter. It also provides the structural support and electrical connection for the meter. This socket must meet stringent utility specification for use with the utility’s meter.

The single phase residential meter is clamped into place by a set of four jaws. The jaws grip the blades in the base of the meter. The jaws also prevent unauthorized tampering with the meter. In some cases, a fifth jaw is required by the utility or metering applications.

Figure 3. (Left to Right) Typical Meter Socket Base, Meter Socket, Jaws

What is a Watt/Hour?

The watt/hour is a standard unit of measurement for electrical power usage. One watt/hour is literally the use of one watt of electricity in one hour.

This is a pretty small amount of electricity. Consider a typical 75-watt light bulb used in a common household table lamp. If that lamp is left on for one hour, it will consume 75 watt/hours of electricity. Now consider all the electrical devices in the average home. The number of watt/hours consumed begin to add up quickly!

For this reason, quantities of electrical power are generally referred to in kilowatt/hours . A Kilowatt/Hour is simply 1,000 watt/hours.

Each of these watt-hour meters is tracking the power consumption in one living unit of this multi-family building.

Watt/Hour Meters

This allows the utility company to bill the occupant of each living unit directly, instead of sending one bill to the building owner.