Квт как пишется мощность

Ватт и киловатт – что это такое

Ватт – это единица измерения мощности, а также потока тепла в физике, потока звукового электричества, мощности постоянного электрического тока, активной и полной мощности электрического тока, потока излучения и потока энергии ионизирующего излучения в международной системе измерения. Следует отметить, что это скалярная измеримая величина, то есть измеряемая и вычисляемая.

Описание из ссылки

Чтобы сделать использование ватт удобным, международная система приняла использование префиксов, которые определяют десятичное число, кратное исходному индикатору. Обычно для этого используется один киловатт. В переводе с греческого приставка килограмм означает тысячу. Использование префикса означает увеличение исходной стоимости в 103 раза.

Примечание! КВт в час – это несистемная единица измерения, которая показывает, когда энергия производится или потребляется и в каком количестве. Он также показывает выполненную механическую работу и температуру. Используется для измерения потребления электроэнергии в домашних хозяйствах или для измерения производства электроэнергии в энергетическом секторе.

Как правильно переводить эти единицы

Ватт равен килограмму на квадратный метр, разделенному на кубические секунды. Приставка кило означает умножение на 1000. Тот же принцип применяется к индикаторам мощности, то есть 1 кВт равен 1000 Вт и 1000 вольт. Это означает, что 1 единица = 0,001 субъединицы. То есть, если сделать передачу мощности, электроприбор на 3 кВт будет равен 3000 Вт.

Вам будет интересно, на какую мощность рассчитан станок 16а
Формула перевода

В электричестве

Для упрощения измерений в электричестве используется подблок. Вы можете узнать, сколько ватт в киловаттах, и преобразовать единицы, умножив ватты на 103 и разделив на 1000. Для выполнения обратного преобразования вам необходимо умножить киловатты на 103 или умножить известные показатели на 1000.

Сумма в электричестве

В отоплении

Для измерения тепловой мощности необходимо использовать джоули. Это работа, которую проделывает 1 ньютон на 1 метр. Чтобы преобразовать джоули в киловатты, вам нужно использовать субъединицу джоулей. В 1 кДж содержится 0,239 ккал. В 1 ккал 4,1868 кДж. В 1 кВт содержится 860 ккал. Это означает, что 1000 ккал – это 1163 кВт в час.

Тепловые меры

Конвертор

Для расчета значений вы можете использовать простой в использовании конвертер. Конвертер – это система, преобразующая исходные данные в заданное значение. Все, что требуется от пользователя, – это ввести существующие данные в поле и нажать кнопку запуска на используемом сервисе.

Примечание! Существуют различные системные преобразователи. Некоторые переводят эти ватты, другие прямо в киловатты.

Конвектор

Таблица переводов единицы ватт в киловатт

Значения измерений, представленные в таблице ниже, помогут вам рассчитать энергию, используемую конкретным устройством, и выполнить другие математические вычисления в области электротехники.

Стол

В общем, киловатт – это подзначение ватта, символ, представляющий мощность. Вы можете правильно перевести Вт в кВт в электричество и тепло, используя формулу пересчета, таблицу и специальный онлайн-калькулятор.

Формула перевода кВА в кВт

где это находится:
P-активная мощность (кВт),
Полная мощность S (кВА),
Os f- коэффициент мощности

Оказывается, чтобы преобразовать кВА в кВт, нужно отнять 20% от кВА, и вы получите кВт с ошибкой, которую можно просто не заметить.

Например, для преобразования мощности 100 кВА в кВт требуется 100 кВА * 0,8 = 80 кВт или 100 кВА-20% = 80 кВт.

Как перевести мощность из кВт в кВА?

где это находится:
Полная мощность S (кВА),
P-активная мощность (кВт),
Os f- коэффициент мощности

Например, чтобы преобразовать мощность 800 кВт в кВА, она должна быть 800 кВт / 0,8 = 1000 кВА.

Отличие киловатт от киловатт∙час

В электротехнике есть величина, называемая киловатт-часом, которую измеряют электросчетчиками. Многие подменяют понятия, не видя разницы между определениями «киловатт» и «киловатт ∙ час», рассматривая значения как параметр.

Несмотря на схожесть названий, это совершенно разные ценности. Киловатт ∙ час используется для измерения количества электроэнергии, произведенной или потребленной в единицу времени. В частности, потребление электроэнергии пользователем мощностью 1 кВт ∙ час указывает на энергию, потребляемую пользователем мощностью 1 кВт за 1 час. И наоборот, киловатт – это единица мощности, которая указывает скорость производства или потребления электроэнергии.

Пример: встраиваемый светодиодный светильник оснащен светодиодной лампой мощностью 35 Вт. За 1 час работы потребляет 35 Вт ∙ час электроэнергии, на 2 часа соответственно 2х35 = 70 Вт ∙ час. При непрерывной работе 5 дней / 120 часов потребляемая мощность светильника составит 35×120 = 4200 Вт ∙ час или 4,2 кВт ∙ час.

Соотношение с основными и кратными единицами мощности

Ватт относится к производной единице измерения мощности, поэтому на практике иногда необходимо определять значение параметра по отношению к основным единицам международной системы СИ. В технических расчетах используются следующие соответствия основным значениям:

• W = кгм² / с³;
• L = Гм / с;
• W = VA

Параметр имеет универсальное применение и одинаково используется в технических разработках различных сфер деятельности.

Теплотехника использует единицы, не входящие в систему СИ, для измерения тепловой мощности в 1 кал / час. Наше рассмотренное значение связано с ним соотношением: 1 Вт = 859,85 кал / час.

Часто для удобства работы с большими значениями мощности электростанций и групп мощности слово ват может использоваться с приставками «мега» или «гига»:

• мегаватт обозначается MW / MW и соответствует 106 Вт;
• гигаватт (сокращенно GW / GW) равен 109 Вт.

Напротив, в слаботочных информационных сетях, электронных устройствах и современном электронном оборудовании мощность измеряется долями ватт:

• милливатты (мВт, мВт) – 10-3 Вт;
• микроватты (мкВт, мкВт) равны 10-6 Вт.

Используя эти соотношения, всегда можно перевести большинство параметров в требуемые силовые агрегаты.

Как посчитать общую мощность бытовых приборов

Установленная мощность дома или коттеджа важна при расчете и выборе электропроводки и машин. Без этого параметра невозможно спроектировать электроснабжение дома.

Чтобы узнать установленную мощность, нужно выбрать данные о потреблении энергии из паспортов оборудования. Например, как указано на номерном знаке.

Имя	Мощность, Вт
Телевидение	150
Водонагреватель	1,500
Электрическая духовка	2 000
Светильники (общее количество лампочек по всему дому)	1,000
Компьютер	100
ОБЩИЙ:	3,750 Вт или 3,75 кВт

Для правильного расчета электроснабжения дома учитывается коэффициент комбинации. Указывает, сколько потребителей работают одновременно.

Для установленной мощности в доме, коттедже, квартире до 14 кВт в расчетах используется коэффициент 0,8. То есть берется общая величина нагрузок и умножается на 0,8. Для нашего примера для расчетов требуется мощность 3,75 * 0,8 = 3 кВт.

Понятие Ватт

Ватт – это единица электроэнергии, которую устройство потребляет за определенный период времени, обычно за 1 час работы. И 1 ватт также равен 1 Дж за 1 секунду.

Перевод ватт в кВт

Например, на утюге написано 2000 Вт (Вт), это означает 2 кВт, другой пример с лампочкой на 100 Вт, при преобразовании в кВт получаем 0,1 кВт, поэтому:

1 кВт = 1000 Вт

По аналогии можно перевести и другие значения:

Вы также можете перевести 1, 2, 3, 4, 5, 6, 7, 8 кВт и т.д. В ватты:

Мощность (Вт) Мощность (кВт)

1000	1
2000 г	2
3000	3
4000	4
5000	5
6000	6
7000	7
8000	восемь

Суммарная мощность

Чтобы определить общую мощность электроприборов в вашем доме, вам нужно сложить мощность всех электроприборов в системе, например, ватты или кВт. Общая мощность обычно рассчитывается для:

1. Правильный выбор сечения провода.
2. Правильный подбор приборов контроля, счетчиков, автоматов и т.д.

kilowatt-hour
Residential electricity meter located in Canada
General information
Unit system	Non-SI metric
Unit of	Energy
Symbol	kW⋅h or kW h
Conversions
1 kW⋅h in …	… is equal to …
SI units	3.6 MJ
CGS units	3.6×1013 erg
English Engineering units	≈ 2,655,224 ft⋅lbf
British Gravitational units	≈ 85,429,300 ft⋅pdl

A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common billing unit for electrical energy delivered to consumers by electric utilities.

Definition[edit]

The kilowatt-hour is a composite unit of energy equal to one kilowatt (kW) sustained for (multiplied by) one hour. Expressed in the standard unit of energy in the International System of Units (SI), the joule (symbol J), it is equal to 3,600 kilojoules or 3.6 MJ.^[1][2]

Unit representations[edit]

A widely used representation of the kilowatt-hour is «kWh», derived from its component units, kilowatt and hour. It is commonly used in billing for delivered energy to consumers by electric utility companies, and in commercial, educational, and scientific publications, and in the media.^[3][4] It is also the usual unit representation in electrical power engineering.^[5] This common representation, however, does not comply with the style guide of the International System of Units (SI).^[6]

Other representations of the unit may be encountered:

• «kW⋅h» and «kW h» are less commonly used, but they are consistent with the SI. The SI brochure^[6] states that in forming a compound unit symbol, «Multiplication must be indicated by a space or a half-high (centred) dot (⋅), since otherwise some prefixes could be misinterpreted as a unit symbol.» This is supported by a voluntary standard^[7] issued jointly by an international (IEEE) and national (ASTM) organization, and by a major style guide.^[8] However, the IEEE/ASTM standard allows «kWh» (but does not mention other multiples of the watt-hour). One guide published by NIST specifically recommends against «kWh» «to avoid possible confusion».^[9]
• The United States official fuel-economy window sticker for electric vehicles uses the abbreviation «kW-hrs».^[10]
• Variations in capitalization are sometimes encountered: KWh, KWH, kwh, etc., which are inconsistent with the International System of Units.
• The notation «kW/h» for the kilowatt-hour is incorrect, as it denotes kilowatt per hour.

The hour is a unit of time listed among the non-SI units accepted by the International Bureau of Weights and Measures for use with the SI.^[6] Its combination with the kilowatt, a standard SI unit, is therefore permitted within the standard.^{[dubious – discuss]}

An electric heater consuming 1,000 watts (1 kilowatt), and operating for one hour uses one kilowatt-hour of energy. A television consuming 100 watts operating continuously for 10 hours uses one kilowatt-hour. A 40-watt electric appliance operating continuously for 25 hours uses one kilowatt-hour.

Electricity sales[edit]

Electrical energy is typically sold to consumers in kilowatt-hours. The cost of running an electrical device is calculated by multiplying the device’s power consumption in kilowatts by the operating time in hours, and by the price per kilowatt-hour. The unit price of electricity charged by utility companies may depend on the customer’s consumption profile over time. Prices vary considerably by locality. In the United States prices in different states can vary by a factor of three.^[11]

While smaller customer loads are usually billed only for energy, transmission services, and the rated capacity, larger consumers 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 changes.^[12] Industrial users may also have extra charges according to the power factor of their load.

Major energy production or consumption is often expressed as terawatt-hours (TWh) for a given period that is often a calendar year or financial year. A 365-day year equals 8,760 hours, so over a period of one year, power of one gigawatt equates to 8.76 terawatt-hours of energy. Conversely, one terawatt-hour is equal to a sustained power of about 114 megawatts for a period of one year.

Examples[edit]

In 2020, the average household in the United States consumed 893 kWh per month.^[13]

In terms of human power, a healthy adult male manual laborer performs work equal to about half a kilowatt-hour over an eight-hour day.^[14]

Conversions[edit]

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⋅m2⋅s−2 =	1	2.77778 × 10−4	2.77778 × 10−7	6.241 × 1018	0.239
1 Wh =	3.6 × 103	1	0.001	2.247 × 1022	859.8
1 kWh =	3.6 × 106	1,000	1	2.247 × 1025	8.598 × 105
1 eV =	1.602 × 10−19	4.45 × 10−23	4.45 × 10−26	1	3.827 × 10−20
1 cal =	4.184	1.162 × 10−3	1.162 × 10−6	2.612 × 1019	1

Watt-hour multiples [edit]

All the SI prefixes are commonly applied to the watt-hour: a kilowatt-hour is 1,000 Wh (kWh); a megawatt-hour is 1 million Wh (MWh); a milliwatt-hour is 1/1,000 Wh (mWh) and so on.
The kilowatt-hour is commonly used by electrical energy 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 and the world energy consumption.

Distinguishing between kilowatt-hours (energy) and kilowatts (power)[edit]

Work is the amount of energy transferred to a system; power is the rate of delivery of energy.
Energy is measured in joules, or watt-seconds. Power is measured in watts, or joules per second.

For example, a battery stores energy. When the battery delivers its energy, it does so at a certain power, that is, the rate of delivery of the energy. The higher the power, the quicker the battery’s stored energy is delivered. A higher power output will cause the battery’s stored energy to be depleted in a shorter time period.

Annualized power[edit]

Electric energy production and consumption are sometimes reported on a yearly basis, in units such as megawatt-hours per year (MWh/yr) gigawatt-hours/year (GWh/yr) or terawatt-hours per year (TWh/yr). These units have dimensions of energy divided by time and thus are units of power. They can be converted to SI power units by dividing by the number of hours in a year, about 8766 h/yr.

Thus, 1 GWh/yr = 1 GWh/8766 h ≈ 114.08 kW.

Misuse of watts per hour[edit]

Many compound units for various kinds of rates explicitly mention units of time to indicate a change over time. For example: miles per hour, kilometres per hour, dollars per hour. Power units, such as kW, already measure the rate of energy per unit time (kW=kJ/s). 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, i.e. an acceleration in the delivery of energy. It is used to measure the daily variation of demand (e.g. the slope of the duck curve), or 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.

Other uses of terms such as watts per hour are likely to be errors.^[15][16]

[edit]

Several other units related to kilowatt-hour are commonly used to indicate power or energy capacity or use in specific application areas.

Average annual energy production or consumption can be expressed in kilowatt-hours per year. This is used with loads or output that vary during the year but whose annual totals are similar from one year to the next. For example, it is useful to compare the energy efficiency of household appliances whose power consumption varies with time or the season of the year. Another use is to measure 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 ampere-hour (Ah) to watt-hours (Wh), the ampere-hour value must be multiplied by the voltage of the power source. This value is approximate, since the battery voltage is not constant during its discharge, and because higher discharge rates reduce the total amount of energy that 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 V for Li-ion) that must be used to calculate rather than the device output (for example, usually 5.0 V for USB portable chargers). This results in a 500 mA USB device running for about 3.7 hours on a 2,500 mAh battery, not five hours.

The Board of Trade unit (B.T.U.)^[17] 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.^[18] This should not be confused with a British Thermal Unit (BTU) which is 1055 J.

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.^[19][20]

See also[edit]

• Ampere hour
• Electric vehicle battery
• Electric energy consumption
• IEEE Std 260.1-2004
• Orders of magnitude (energy)

References[edit]

kilowatt-hour
Residential electricity meter located in Canada
General information
Unit system	Non-SI metric
Unit of	Energy
Symbol	kW⋅h or kW h
Conversions
1 kW⋅h in …	… is equal to …
SI units	3.6 MJ
CGS units	3.6×1013 erg
English Engineering units	≈ 2,655,224 ft⋅lbf
British Gravitational units	≈ 85,429,300 ft⋅pdl

A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common billing unit for electrical energy delivered to consumers by electric utilities.

Definition[edit]

The kilowatt-hour is a composite unit of energy equal to one kilowatt (kW) sustained for (multiplied by) one hour. Expressed in the standard unit of energy in the International System of Units (SI), the joule (symbol J), it is equal to 3,600 kilojoules or 3.6 MJ.^[1][2]

Unit representations[edit]

A widely used representation of the kilowatt-hour is «kWh», derived from its component units, kilowatt and hour. It is commonly used in billing for delivered energy to consumers by electric utility companies, and in commercial, educational, and scientific publications, and in the media.^[3][4] It is also the usual unit representation in electrical power engineering.^[5] This common representation, however, does not comply with the style guide of the International System of Units (SI).^[6]

Other representations of the unit may be encountered:

• «kW⋅h» and «kW h» are less commonly used, but they are consistent with the SI. The SI brochure^[6] states that in forming a compound unit symbol, «Multiplication must be indicated by a space or a half-high (centred) dot (⋅), since otherwise some prefixes could be misinterpreted as a unit symbol.» This is supported by a voluntary standard^[7] issued jointly by an international (IEEE) and national (ASTM) organization, and by a major style guide.^[8] However, the IEEE/ASTM standard allows «kWh» (but does not mention other multiples of the watt-hour). One guide published by NIST specifically recommends against «kWh» «to avoid possible confusion».^[9]
• The United States official fuel-economy window sticker for electric vehicles uses the abbreviation «kW-hrs».^[10]
• Variations in capitalization are sometimes encountered: KWh, KWH, kwh, etc., which are inconsistent with the International System of Units.
• The notation «kW/h» for the kilowatt-hour is incorrect, as it denotes kilowatt per hour.

The hour is a unit of time listed among the non-SI units accepted by the International Bureau of Weights and Measures for use with the SI.^[6] Its combination with the kilowatt, a standard SI unit, is therefore permitted within the standard.^{[dubious – discuss]}

An electric heater consuming 1,000 watts (1 kilowatt), and operating for one hour uses one kilowatt-hour of energy. A television consuming 100 watts operating continuously for 10 hours uses one kilowatt-hour. A 40-watt electric appliance operating continuously for 25 hours uses one kilowatt-hour.

Electricity sales[edit]

Electrical energy is typically sold to consumers in kilowatt-hours. The cost of running an electrical device is calculated by multiplying the device’s power consumption in kilowatts by the operating time in hours, and by the price per kilowatt-hour. The unit price of electricity charged by utility companies may depend on the customer’s consumption profile over time. Prices vary considerably by locality. In the United States prices in different states can vary by a factor of three.^[11]

While smaller customer loads are usually billed only for energy, transmission services, and the rated capacity, larger consumers 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 changes.^[12] Industrial users may also have extra charges according to the power factor of their load.

Major energy production or consumption is often expressed as terawatt-hours (TWh) for a given period that is often a calendar year or financial year. A 365-day year equals 8,760 hours, so over a period of one year, power of one gigawatt equates to 8.76 terawatt-hours of energy. Conversely, one terawatt-hour is equal to a sustained power of about 114 megawatts for a period of one year.

Examples[edit]

In 2020, the average household in the United States consumed 893 kWh per month.^[13]

In terms of human power, a healthy adult male manual laborer performs work equal to about half a kilowatt-hour over an eight-hour day.^[14]

Conversions[edit]

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⋅m2⋅s−2 =	1	2.77778 × 10−4	2.77778 × 10−7	6.241 × 1018	0.239
1 Wh =	3.6 × 103	1	0.001	2.247 × 1022	859.8
1 kWh =	3.6 × 106	1,000	1	2.247 × 1025	8.598 × 105
1 eV =	1.602 × 10−19	4.45 × 10−23	4.45 × 10−26	1	3.827 × 10−20
1 cal =	4.184	1.162 × 10−3	1.162 × 10−6	2.612 × 1019	1

Watt-hour multiples [edit]

All the SI prefixes are commonly applied to the watt-hour: a kilowatt-hour is 1,000 Wh (kWh); a megawatt-hour is 1 million Wh (MWh); a milliwatt-hour is 1/1,000 Wh (mWh) and so on.
The kilowatt-hour is commonly used by electrical energy 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 and the world energy consumption.

Distinguishing between kilowatt-hours (energy) and kilowatts (power)[edit]

Work is the amount of energy transferred to a system; power is the rate of delivery of energy.
Energy is measured in joules, or watt-seconds. Power is measured in watts, or joules per second.

For example, a battery stores energy. When the battery delivers its energy, it does so at a certain power, that is, the rate of delivery of the energy. The higher the power, the quicker the battery’s stored energy is delivered. A higher power output will cause the battery’s stored energy to be depleted in a shorter time period.

Annualized power[edit]

Electric energy production and consumption are sometimes reported on a yearly basis, in units such as megawatt-hours per year (MWh/yr) gigawatt-hours/year (GWh/yr) or terawatt-hours per year (TWh/yr). These units have dimensions of energy divided by time and thus are units of power. They can be converted to SI power units by dividing by the number of hours in a year, about 8766 h/yr.

Thus, 1 GWh/yr = 1 GWh/8766 h ≈ 114.08 kW.

Misuse of watts per hour[edit]

Many compound units for various kinds of rates explicitly mention units of time to indicate a change over time. For example: miles per hour, kilometres per hour, dollars per hour. Power units, such as kW, already measure the rate of energy per unit time (kW=kJ/s). 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, i.e. an acceleration in the delivery of energy. It is used to measure the daily variation of demand (e.g. the slope of the duck curve), or 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.

Other uses of terms such as watts per hour are likely to be errors.^[15][16]

[edit]

Several other units related to kilowatt-hour are commonly used to indicate power or energy capacity or use in specific application areas.

Average annual energy production or consumption can be expressed in kilowatt-hours per year. This is used with loads or output that vary during the year but whose annual totals are similar from one year to the next. For example, it is useful to compare the energy efficiency of household appliances whose power consumption varies with time or the season of the year. Another use is to measure 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 ampere-hour (Ah) to watt-hours (Wh), the ampere-hour value must be multiplied by the voltage of the power source. This value is approximate, since the battery voltage is not constant during its discharge, and because higher discharge rates reduce the total amount of energy that 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 V for Li-ion) that must be used to calculate rather than the device output (for example, usually 5.0 V for USB portable chargers). This results in a 500 mA USB device running for about 3.7 hours on a 2,500 mAh battery, not five hours.

The Board of Trade unit (B.T.U.)^[17] 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.^[18] This should not be confused with a British Thermal Unit (BTU) which is 1055 J.

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.^[19][20]

See also[edit]

• Ampere hour
• Electric vehicle battery
• Electric energy consumption
• IEEE Std 260.1-2004
• Orders of magnitude (energy)

References[edit]