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Physics 13.3.3a - The Kilowatt hour

Published: 2009/09/27

Channel: Derek Owens

What is a Kilowatt Hour?

Published: 2013/11/27

Channel: ONgov

What's the difference between a kW and a kWh?

Published: 2012/04/11

Channel: ASUEnergyPolicy

GCSE Physics Revision: Kilowatt-hours.

Published: 2015/04/13

Channel: Freesciencelessons

What Is A Kilowatt-Hour?

Published: 2014/03/28

Channel: oppdweb

Explanation of how kilowatt-hour meters work (electromechanical)

Published: 2013/10/06

Channel: Applied Science

What is a Kilowatt-hour?

Published: 2013/03/13

Channel: Highland Science

A Level Physics - The Kilowatt Hour

Published: 2015/05/21

Channel: A Level Physics Online

Solar Sunday 0003: My First Kilowatt-Hour

Published: 2014/11/08

Channel: Rinoa Super-Genius

How To Compute Kwh

Published: 2011/04/06

Channel: Two-Point-Four

Erin Explains Energy – kilowatts vs kilowatt hours

Published: 2015/11/10

Channel: Western Resource Advocates

Analog Kilowatt hour (KWH) meter teardown and explanation of operation

Published: 2013/06/08

Channel: Jacob Dykstra

how to calculate kwh - electrical formulas

Published: 2014/10/16

Channel: Electrical videos

how to calculate watts to kwh - electrical formulas

Published: 2014/10/17

Channel: Electrical videos

Kilowatt hour Problems

Published: 2014/01/20

Channel: Emily Kroutil

Calculating Average Price per Kilowatt Hour

Published: 2012/09/28

Channel: txuenergy

GCSE Physics Revision: Kilowatt-hours 2

Published: 2015/04/13

Channel: Freesciencelessons

Calculating the KWH Your Solar Panels Produce

Published: 2016/04/05

Channel: Understand Solar

Solar kW vs kWh

Published: 2014/12/26

Channel: Helios Solar Systems

What are kilowatt hours?

Published: 2011/05/04

Channel: energyhelpline

The Kilowatt Hour, Bologna 24-09-2013

Published: 2013/09/25

Channel: Massimiliano Scordamaglia

P3.3 Kilowatt hours and the cost of electricity

Published: 2015/04/17

Channel: MissLowePhysics

AP Physics 1 & 2: Circuits 9: Kilowatt-hour: kWh

Published: 2013/02/11

Channel: Yau-Jong Twu

Conversion of Horsepower HP to Kilowatt Hours KWH

Published: 2015/06/29

Channel: Wastewater Dan

Kilowatt-hour Meaning

Published: 2015/04/18

Channel: SDictionary

What is the difference between a kilowatt and a kilowatt-hour?

Published: 2012/10/05

Channel: One Block Off the Grid

Old Kilowatt Hour Meters - Running

Published: 2012/01/09

Channel: More350Power

What Is A Kilowatt-Hour?

Published: 2016/06/24

Channel: Pick My Solar Corporate Office

Kilowatts, Kilowatt-Hours and Peak Kilowatts - kW, kWh, kWp

Published: 2016/04/14

Channel: Understand Solar

How to read your electric meter

Published: 2008/09/14

Channel: nlcpr001

If electrical energy costs $0.12 per kilowatt-hour, how much does it cost to (a) burn a 100-W lightb

Published: 2016/02/09

Channel: WNY Tutor

Energy Video kWH J BTU relationship

Published: 2012/05/07

Channel: TutenFHS

Driving Down the Dollars per Kilowatt Hour Cost

Published: 2012/06/04

Channel: AutomotiveDigest

Sangamo SPA01 Single Phase Kilowatt Hour Meter

Published: 2012/12/26

Channel: Bi Lock 102

Earth Hour 2013 One kilowatt Hour by Shenzhen Power Supply Co. Ltd

Published: 2013/06/17

Channel: Earth Hour

How to Convert Cubic Feet to Kilowatt Hours : Fractions & Other Math Tips

Published: 2013/08/28

Channel: eHowEducation

Technical Terms, kWh and kVA

Published: 2012/11/24

Channel: Hannes Roets

How to Convert One Cubic Foot of Gas to Kilowatt-Hours : Conversions & Other Math Tips

Published: 2013/01/19

Channel: eHowEducation

What is a kilowatt-hour?

Published: 2016/06/21

Channel: Regency Lighting

Email M 3 Kilowatt hour meter

Published: 2011/07/22

Channel: RODALCO2007

Why do we measure electricity consumption in kilowatt-hours?

Published: 2013/04/27

Channel: Because We Can- The Channel

MITO 2013 Milano - The Kilowatt Hour

Published: 2013/09/20

Channel: mitosettembremusica

Sangamo SPA 01 kilowatthour meter

Published: 2011/07/28

Channel: RODALCO2007

Peach Dynamo - Kilowatt hour

Published: 2016/03/13

Channel: Peach Dynamo

Defining KiloWatt Hour - Algebra Based Physics

Published: 2013/01/10

Channel: thomaspalmerphysics

San Diego Kilowatt Hour E-bike Ride---Mission Bay

Published: 2013/02/03

Channel: TurboBobsBicycleBlog

Commercial Unit Of Energy KiloWatt Hour KWh

Published: 2012/11/27

Channel: sardanatutorials

Home Energy Ed - kwh

Published: 2010/10/14

Channel: energyflair

San Diego Electric Bike Hosts the Kilowatt Hour E-bike Ride

Published: 2013/07/20

Channel: TurboBobsBicycleBlog

UB: Mahigit P4 kada kilowatt hour na dagdag-singil ng Meralco, tuloy na tuloy na

Published: 2013/12/09

Channel: GMA News and Public Affairs

From Wikipedia, the free encyclopedia

"KWH" redirects here. For other uses, see KWH (disambiguation).

The **kilowatt hour** (symbol **kWh**, **kW·h**, or **kW h**) is a derived unit of energy equal to 3.6 megajoules.^{[1]}^{[2]} If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time in hours. The kilowatt-hour is commonly used as a billing unit for energy delivered to consumers by electric utilities.

The kilowatt-hour (symbolized kW⋅h) is a unit of energy equivalent to one kilowatt (1 kW) of power sustained for one hour.

One watt is equal to 1 J/s. One kilowatt-hour is 3.6 megajoules, which is the amount of energy converted if work is done at an average rate of one thousand watts for one hour.

Note that the international standard SI unit of energy is the joule. The hour is a unit of time "outside the SI",^{[3]} so the kilowatt-hour is a non-SI unit of energy. It is not listed among the non-SI units accepted by the BIPM for use with the SI.

An electric heater rated at 1000 watts (1 kilowatt), operating for one hour uses one kilowatt-hour (equivalent to 3.6 megajoules) of energy. A television rated at 100 watts operating for 10 hours continuously uses one kilowatt-hour. A 40-watt light bulb operating continuously for 25 hours uses one kilowatt-hour.

Electrical energy is sold in kilowatt-hours; cost of running equipment is the product of power in kilowatts multiplied by running time in hours and price per kilowatt-hour. The unit price of electricity may depend upon the rate of consumption and the time of day. Industrial users may also have extra charges according to their peak usage and the power factor.

The symbol "**kWh**" is commonly used in commercial, educational, scientific and media publications,^{[4]} and is the usual practice in electrical power engineering.^{[5]}

Other abbreviations and symbols may be encountered:

- "kW h" is less commonly used. It is consistent with SI standards (but note that the kilowatt-hour is a non-SI unit). The international standard for SI
^{[3]}states that in forming a compound unit symbol, "Multiplication must be indicated by a space or a half-high (centered) dot (·), since otherwise some prefixes could be misinterpreted as a unit symbol" (i.e., kW h or kW·h). This is supported by a voluntary standard^{[6]}issued jointly by an international (IEEE) and national (ASTM) organization. However, at least one major usage guide^{[7]}and the IEEE/ASTM standard allow "kWh" (but do not mention other multiples of the watt hour). One guide published by NIST specifically recommends avoiding "kWh" "to avoid possible confusion".^{[8]} - The US official fuel-economy window sticker for electric vehicles uses the abbreviation "kW-hrs".
^{[9]} - Variations in capitalization are sometimes seen: KWh, KWH, kwh, etc. these are inconsistent with International System of Units.
- "kW·h" is, like "kW h", preferred with SI standards, but it is very rarely used in practice.
- The notation "kW/h", as a symbol for kilowatt-hour, is not correct.

Further information: Conversion of units of energy

To convert a quantity measured in a unit in the left column to the units in the top row, multiply by the factor in the cell where the row and column intersect.

joule | watt hour | kilowatt hour | electronvolt | calorie | |
---|---|---|---|---|---|

1 J = 1 kg·m^{2} s^{−2} = |
1 | 2.77778 × 10^{−4} |
2.77778 × 10^{−7} |
6.241 × 10^{18} |
0.239 |

1 W·h = | 3,600 | 1 | 0.001 | 2.247 × 10^{22} |
859.8 |

1 kW·h = | 3.6 × 10^{6} |
1,000 | 1 | 2.247 × 10^{25} |
8.598 × 10^{5} |

1 eV = | 1.602 × 10^{−19} |
4.45 × 10^{−23} |
4.45 × 10^{−26} |
1 | 3.827 × 10^{−20} |

1 cal = | 4.1868 | 1.163 × 10^{−3} |
1.163 × 10^{−6} |
2.613 × 10^{19} |
1 |

The kilowatt-hour is commonly used by electrical distribution providers for purposes of billing, since the monthly energy consumption of a typical residential customer ranges from a few hundred to a few thousand kilowatt-hours. **Megawatt-hours** (**MWh**), **gigawatt-hours** (**GWh**), and **terawatt-hours** (**TWh**) are often used for metering larger amounts of electrical energy to industrial customers and in power generation. The terawatt-hour and **petawatt-hour** (**PWh**) units are large enough to conveniently express the annual electricity generation for whole countries.

Submultiples | Multiples | |||||
---|---|---|---|---|---|---|

Value | Symbol | Name | Value | Symbol | Name | |

10^{−3} |
mW·h | milliwatt hour | 10^{3} |
kW·h | kilowatt hour | |

10^{−6} |
µW·h | microwatt hour | 10^{6} |
MW·h | megawatt hour | |

10^{9} |
GW·h | gigawatt hour | ||||

10^{12} |
TW·h | terawatt hour | ||||

10^{15} |
PW·h | petawatt hour |

The terms power and energy are frequently confused. Power is defined as work per unit time, measured in units *joules per second* or *watts*. To produce power over any period of time requires energy. Either higher levels of power for a given period or longer periods of run time at a given power level require more energy.

An electrical load, e.g. a lamp, toaster, electric motor, has a rated size in watts. This is its running power level, which equates to the instantaneous rate at which energy must be generated and consumed to run the device. The amount of energy that is consumed at that rate depends on how long the device is operated. However, its power requirements are constant while running. The unit of energy for residential electrical billing, *kilowatt-hours*, integrates changing power levels in use at the residence over the past billing period, which is nominally 720 hours for a 30-day month, thus showing cumulative electrical energy use for the month.

For another example, when a light bulb with a power rating of 100 watts is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt-hour, or 360 kilojoules. This same amount of energy would light a 40-watt bulb for 2.5 hours, or a 10-watt low-energy bulb for 10 hours. A power station electricity output at any particular moment would be measured in multiples of watts, but its annual energy sales would be in multiples of watt-hours. A kilowatt-hour is the amount of energy equivalent to a steady power of 1 kilowatt running for 1 hour, or 3.6 megajoules.

Energy cost can be illustrated in a similar example: a 100-watt (i.e. 0.1 kilowatt) light bulb turned on for 8 hours uses 800 W⋅h or 0.8 kW⋅h. If the energy cost is 25 cents per kilowatt-hour, it would cost 0.1 kW × 8 h × $0.25/kW⋅h = $0.20.

Whereas individual homes only pay for the kilowatt-hours consumed, commercial buildings and institutions also pay for peak power consumption, the greatest power recorded in a fairly short time, such as 15 minutes. This compensates the power company for maintaining the infrastructure needed to provide peak power. These charges are billed as demand charges.^{[10]}

Major energy production or consumption is often expressed as terawatt-hours (TW⋅h) for a given period that is often a calendar year or financial year. One terawatt-hour is equal to a sustained power of approximately 114 megawatts for a period of one year.

Power units measure the rate of energy per unit time. Many compound units for rates explicitly mention units of time, for example, miles per hour, kilometers per hour, dollars per hour. Kilowatt-hours are a product of power and time, not a rate of change of power with time. Watts per hour (W/h) is a unit of a *change* of power per hour. It might be used to characterize the ramp-up behavior of power plants. For example, a power plant that reaches a power output of 1 MW from 0 MW in 15 minutes has a ramp-up rate of 4 MW/h. Hydroelectric power plants have a very high ramp-up rate, which makes them particularly useful in peak load and emergency situations.

The proper use of terms such as *watts per hour* is uncommon, whereas misuse^{[11]} may be widespread.

Several other units are commonly used to indicate power or energy capacity or use in specific application areas. All the SI prefixes are commonly applied to the watt-hour: a kilowatt-hour is 1,000 W·h (symbols kW·h, kWh or kW h; a megawatt-hour is 1 million W·h, (symbols MW·h, MWh or MW h); a milliwatt-hour is 1/1000 W·h (symbols mW·h, mWh or mW h) and so on.

Average annual power production or consumption can be expressed in kilowatt-hours per year; for example, when comparing the energy efficiency of household appliances whose power consumption varies with time or the season of the year, or the energy produced by a distributed power source. One kilowatt-hour per year equals about 114.08 milliwatts applied constantly during one year.

The energy content of a battery is usually expressed indirectly by its capacity in ampere-hours; to convert watt-hours (W·h) to ampere-hour (A·h), the watt-hour value must be divided by the voltage of the power source. This value is approximate, since the voltage is not constant during discharge of a battery, and because higher discharge rates reduce the total amount of energy the battery can provide. In the case of devices that output a different voltage than the battery, it is the battery voltage (typically 3.7 for Li-ion) that must be used to calculate rather than the device output (usually 5.0 for USB portable chargers), since use of the lower figure allows manufacturers of such devices to overstate the capacity or run-time, inflating it by 35% (^{5}⁄_{3.7}=1.35). This results in a 500mA USB device running for only about 3.7 hours on a 2500mAh battery, rather than the expected five hours.

The *Board of Trade unit* (BOTU) is an obsolete UK synonym for kilowatt-hour. The term derives from the name of the Board of Trade which regulated the electricity industry until 1942 when the Ministry of Power took over.^{[12]} The B.O.T.U. should not be confused with the British thermal unit or BTU, which is a much smaller quantity of thermal energy.

In India, the kilowatt-hour is often simply called a *Unit* of energy. A million units, designated *MU*, is a gigawatt-hour and a BU (billion units) is a terawatt-hour.^{[13]}^{[14]}

Burnup of nuclear fuel is normally quoted in megawatt-days per tonne (MW·d/MTU), where tonne refers to a metric ton of uranium metal or its equivalent, and megawatt refers to the entire thermal output, not the fraction which is converted to electricity.^{[citation needed]}

**^**Thompson, Ambler and Taylor, Barry N. (2008).*Guide for the Use of the International System of Units (SI)*(Special publication 811). Gaithersburg, MD: National Institute of Standards and Technology. 12.**^**"Half-high dots or spaces are used to express a derived unit formed from two or more other units by multiplication." Barry N. Taylor. (2001 ed.)*The International System of Units.*(Special publication 330). Gaithersburg, MD: National Institute of Standards and Technology. 20.- ^
^{a}^{b}The International System of Units (SI). (2006, 8th ed.) Paris: International Bureau of Weights and Measures. 130. **^**See for example:*Wind Energy Reference Manual Part 2: Energy and Power Definitions*Danish Wind Energy Association. Retrieved 9 January 2008; "Kilowatt-Hour (kWh)" BusinessDictionary.com. Retrieved 9 January 2008; "US Nuclear Power Industry" www.world-nuclear.org. Retrieved 9 January 2008; "Energy. A Beginners Guide: Making Sense of Units"*Renew On Line (UK)*. The Open University. Retrieved 9 January 2008. Archived November 26, 2007, at the Wayback Machine.**^**ASTM SI10-10, IEEE/ASTM SI 10 American National Standard for Metric Practice, ASTM International, West Conshohocken, PA, 2010, [www.astm.org] "The symbols for certain compound units of electrical power engineering are usually written without separation, thus: watthour (Wh), kilowatthour (kWh), voltampere (VA), and kilovoltampere (kVA)"**^***Standard for the Use of the International System of Units (SI): The Modern Metric System. (1997). (IEEE/ASTM SI 10-1997). New York and West Conshohocken, PA: Institute of Electrical and Electronics Engineers and ASTM. 15.***^***Chicago Manual of Style*. (14th ed., 1993) University of Chicago Press. 482.**^**Guide for the Use of the International System of Units (SI) p.12**^**"Electric Vehicles: Learn More About the New Label".*fueleconomy.gov*. US Department of energy. Retrieved 10 August 2014.**^**" Understanding Electric Demand", National Grid**^**"Inverter Selection". Northern Arizona Wind and Sun. Retrieved 27 March 2009.**^**"The Board of Trade 1621-1970". Archived from the original on 2010.**^**"Get enlightened about electricity".*The Financial Express*. December 20, 2004. Retrieved 29 November 2009.^{[dead link]}**^**"BHEL manufactured units generate record power".*The Hindu*. Press Trust of India. July 24, 2008. Retrieved 29 November 2009.^{[dead link]}

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