Electricity is commonly measured by its:
- Strength or force as it moves through electric wiring (measured in volts)
- Current or flow (measured in amperes)
While the term volt is a measurement unit of electrical pressure, voltage refers to the strength or force from an electric power source. The higher the voltage rating of a source, the greater the amount of electric power that comes from it. Some common examples of voltage include a small battery (9 volts), a car battery (12 volts) or the electric power that comes into your home (120 or 240 volts). Of course, the strength or power of the electric source from the car battery is much stronger than that from the 9-volt battery. Similarly, the power of the electric source from an electrical outlet is much stronger than that from a car battery.
An amp is a unit that measures the strength/rate of flow of electrical current. The term Amperes refers to the amount of electric flow or current that is transmitted through electric wiring or devices. The higher the amperage rating, the greater the amount of electric flow or current that is being conducted through a wire or device. For example, an electric current of 20 amps is much greater than 5 amps.
A watt is an electrical unit of power. This term is commonly used to rate appliances using relatively small amounts of electricity. Wattage is stamped on light bulbs and all appliances. Wattage = Amps x Voltage.
Like watts, kilowatts refer to the amount of power used by an electrical device. Because the term kilo is an abbreviation for one thousand, a kilowatt is another way of saying 1,000 watts. The abbreviation for kilowatt is kW. In more practical terms, when ten 100-watt light bulbs are turned on at the same time, they use 1,000 watts of electric power (10 bulbs x 100 watts = 1,000 watts).
If ten 100-watt light bulbs stay on for one hour, they will use one kilowatt-hour. If they were allowed to stay on for two hours, this would be two kilowatt-hours, and so on. Kilowatt-hour is the term used to measure and bill the amount of electric energy used.