An electric power meter is a device that measures electricity usage. Meters are used by utility companies for billing purposes and they also can be used by individuals to monitor their power consumption. Companies that offer energy audits employ meters in their work, as do law enforcement agencies that may use power consumption as a tool for identifying areas where criminal activity may be occurring.
One type of electric power meter that many people are familiar with is the electric use meter fitted by utilities. The meter is positioned at the location of the service drop, the point where a structure connects to the electricity grid. When power is needed, it goes through the meter, triggering a device that tracks power consumption over time. The meter doesn't monitor how the power is used, only how much is used, and is read by utility personnel who record the data so that the customer can be billed.
There are legal penalties for tampering with the meter installed by a utility. Although property owners are responsible for buying the equipment and hiring a licensed electrician to install it, only the utility has the authority to reset or otherwise alter and adjust the meter. Utilities must be contacted when doing work on the meter and connected circuit or fuse box so they can cut power to the structure. It may be necessary to have the approval of an electrical inspector to restore power after the work is finished.
Another type of electric power meter can be used with a specific device or on a particular outlet. People can use meters to find out how much energy things use, to track energy usage, or to identify inefficient devices. In this case, the meter plugs into the outlet and the device plugs into the electric power meter. When the device draws energy, it moves through the meter and the amount of power used is recorded. These types of devices can be useful for diagnosis of electrical problems, as well as studies determining power consumption associated with various appliances.
When an energy audit is conducted, an electric power meter may be used to identify problem appliances and other devices. Comparing power consumption, people can decide which devices should be replaced or make other adjustments, such as unplugging devices when not in use. Electricians may also use power meters for similar activities when conducting inspections and repairs.