Browse Definitions:
Definition

# watt-hour (Wh)

The watt-hour (symbolized Wh) is a unit of energy equivalent to one watt (1 W) of power expended for one hour (1 h) of time. The watt-hour is not a standard unit in any formal system, but it is commonly used in electrical applications.

An energy expenditure of 1 Wh represents 3600 joules (3.600 x 103 J). To obtain joules when watt-hours are known, multiply by 3.600 x 103. To obtain watt-hours when joules are known, multiply by 2.778 x 10-4.

In general, energy (E) is equivalent to power (P) multiplied by time (t). To determine E in watt-hours, P must be expressed in watts and t must be expressed in hours. Suppose a 60-W bulb burns for 3 h. Then P = 60 and t = 3, so the energy E in watt-hours is:

E = Pt = 60 x 3 = 180 Wh

If P and t are not specified in watts and hours respectively, then they must be converted to those units before determining E in watt-hours.

The watt-hour is rarely used to express energy in any form other than electrical. A quantity of gasoline, oil, or coal contains potential energy that is liberated when the fuel is burned. The heat energy resulting from combustion of such fuels is usually expressed in joules according to the International System of Units (SI) or in British thermal units (Btu) according to the foot-pound-second (fps) or English system. If this energy is used to operate an electric generator, the output of the generator over a certain period of time can be expressed in watt-hours.

Compare kilowatt-hour. Also see energy, joule, International System of Units (SI), and Table of Physical Units.

This was last updated in September 2005

#### Start the conversation

Send me notifications when other members comment.

## SearchCompliance

• ### risk map (risk heat map)

A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces.

• ### internal audit (IA)

An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

• ### pure risk (absolute risk)

Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...

## SearchSecurity

• ### FIDO (Fast Identity Online)

FIDO (Fast ID Online) is a set of technology-agnostic security specifications for strong authentication. FIDO is developed by the...

• ### cryptanalysis

Cryptanalysis is the study of ciphertext, ciphers and cryptosystems with the aim of understanding how they work and finding and ...

• ### Trojan horse (computing)

In computing, a Trojan horse is a program that appears harmless, but is, in fact, malicious.

## SearchHealthIT

• ### vendor neutral archive (VNA)

A vendor neutral archive (VNA) is a technology that stores medical images in a standard format and interface, making them ...

• ### HITECH (Health Information Technology for Economic and Clinical Health) Act of 2009

The HITECH (Health Information Technology for Economic and Clinical Health) Act of 2009 is legislation that was created to ...

• ### Epic Systems

Epic Systems is one of the largest providers of health information technology, used primarily by large U.S. hospitals and health ...

## SearchDisasterRecovery

• ### business continuity and disaster recovery (BCDR)

Business continuity and disaster recovery (BCDR) are closely related practices that describe an organization's preparation for ...

• ### business continuity plan (BCP)

A business continuity plan (BCP) is a document that consists of the critical information an organization needs to continue ...

• ### call tree

A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...

## SearchStorage

• ### cloud storage provider

A cloud storage provider, also known as a managed service provider (MSP), is a company that offers organizations and individuals ...

• ### personal cloud storage (PCS)

Personal cloud storage (PCS) enables users to store data, photos, music, videos and other files on a local network-attached ...

• ### cloud SLA (cloud service-level agreement)

A cloud SLA (cloud service-level agreement) is an agreement between a cloud service provider and a customer that ensures a ...

## SearchSolidStateStorage

• ### hybrid hard disk drive (HDD)

A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.

Close