Kilowatt-Hour
A kilowatt-hour (kWh) is a unit of measurement that quantifies energy consumption over time, specifically representing the amount of energy used when a device with a power rating of one kilowatt operates for one hour. It is commonly utilized in households to measure electrical energy usage, allowing consumers to understand their energy bills and consumption patterns. For instance, a 1,000-watt appliance, like a toaster, will consume one kilowatt-hour if used continuously for one hour.
The kilowatt-hour is a practical measure, enabling comparison of energy efficiency among different devices or changes in energy usage over time. Although not an SI unit, it is widely recognized and serves as a standard for electricity billing. Other energy units, such as calories in chemistry or electron volts in physics, may be more common in specific contexts, but the kilowatt-hour remains a central metric in discussions about household power consumption and energy efficiency. Overall, understanding kilowatt-hours can help individuals make informed decisions about their energy use and costs.
Kilowatt-Hour
FIELDS OF STUDY: Thermodynamics; Electronics
ABSTRACT: The kilowatt-hour (sometimes "kilowatt hour") is a unit of measure for electricity consumption. It is equal to the consumption of 1,000 watts of power over the course of one hour.
PRINCIPAL TERMS
- calorie: the amount of energy needed to raise the temperature of one gram of water by one degree Celsius (1.8 degrees Fahrenheit) at one atmosphere of pressure, equivalent to approximately 4.2 joules.
- consumed energy: the amount of energy used or transferred over a period of time, often measured in kilowatt-hours.
- electron volt: the amount of energy carried by a single electron moved across an electric potential difference of one volt; equal to 1.6 x 10−19 joules.
- energy: the ability of a system to perform work.
- International System of Units (SI): a standardized system of units and measures based on the metric system.
- joule: the SI unit of energy, work, or heat; equivalent to the work done by one newton of force moving one meter.
- kilowatt: a unit measuring work over time, equivalent to 1,000 watts, or joules per second
- power: energy over time; describes rate of work and measured in joules per second.
Watts to Kilowatt-hours
The International System of Units (SI) is a global measurement system used in science and other disciplines. The watt (W) is an SI derived unit of power, or energy used over time. One watt is equal to one joule per second. The joule is another SI derived unit equal to the work of one newton of force moving a distance of one meter. Household appliances have labels that state how many watts each device uses. For example, a 60 W light bulb uses 60 joules of electrical energy per second and turns most of that energy into light and heat. The kilowatt-hour (kWh) measures the rate of energy consumption in wattage over time, in terms of kilowatts (kW) per hour. Unlike the watt and the joule, the kilowatt and kilowatt-hour are not SI units.
Units of Electricity and Energy
The kilowatt-hour is a familiar method of measuring the rate of energy used over time, but other measures exist. The measurement of time is always in units of seconds, minutes, and hours, but the units of energy vary by area of study and convention. In chemistry, the calorie (c) is a popular alternative for measuring energy in fuel sources like coal. In physics, the electron volt (eV) may be used instead. A single electron carries exactly one electron volt of energy when it moves across an electric potential difference of one volt.
How Much Energy Does Your Toaster Use?
A 1,000 W toaster that is used nonstop for one hour would use exactly one kilowatt-hour. The kilowatt-hour is a way to measure the consumed energy of a home over the course of time. The monthly electrical energy consumption of most homes ranges from hundreds to thousands of kilowatt-hours. Because a kilowatt-hour expresses the rate of energy used over time, it is a useful way to compare the efficiency of various homes or the same home over months or years.
Bibliography
Dodge, David. "So What Is a Kilowatt-Hour Anyway?" HuffPost Blog. Huffington Post Media Group, 17 Mar. 2015. Web. 25 Mar. 2015.
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"Estimating Appliance and Home Electronic Energy Use." Energy.gov. US Dept. of Energy, 5 Nov. 2014. Web. 23 Mar. 2015.
"International System of Units (SI)." Encyclopaedia Britannica. Encyclopaedia Britannica, 14 Jul. 2013. Web. 25 Mar. 2015.
Nakagami, Hidetoshi, Murakoshi, Chiharu, and Yumiko Iwafune. "International Comparison of Household Energy Consumption and Its Indicator." ACEEE Summer Study on Energy Efficiency in Buildings. Amer. Council for an Energy-Efficient Economy, 2008. Web. 25 Mar. 2015.
"Residential Sector Energy Consumption." Buildings Energy Data Book. US Dept. of Energy, Mar. 2012. Web. 25 Mar. 2015.