- An hour meter, also known as an electrical meter, is a device which records the amount of power a building or apartment uses, generally for the purpose of charging the user for it. Electrical power is measured in watts. A typical incandescent light bulb, for example, uses from 60 to 100 watts per hour. Electrical power meters record kilowatt-hours - the amount of energy used by a 1,000-watt appliance running for one hour.
- Most electrical meters have small, rotating metal disks inside. When electricity flows into a building, some of it runs into a coil beside the meter. The coil makes a small magnetic field, causing the disk to spin. The speed of the disk is proportional to the amount of current flowing into the house. The more power that flows in, the faster the disk spins.
- The disk spins around a certain number of times for every kilowatt hour used. On mechanical systems like the ones you sometimes see on the sides of buildings, the disk is connected by gears to a dial that spins around once for every kilowatt-hour used. That dial is connected by gears to a second dial that spins 10 times slower, going around once for every 10 kilowatt-hours used. There are further dials for 100, 1,000, and even 10,000 kilowatt-hours. A meter reader has to come out to the house and record these numbers to get the total electrical usage in the building.
- Instead of using a gear drive to record the number of kilowatt-hours used, modern meters count the number electronically using a computer. This computer can also record the power usage at any given moment, the time of day and other information about electrical consumption patterns. This allows electrical companies to charge more money for energy used during peak periods and less at night. Modern meters can also transmit the information they record back to the electric company, eliminating the need for a meter reader.
