Efficiency
Encyclopedia
Efficiency in general describes the extent to which time or effort is well used for the intended task or purpose. It is often used with the specific purpose of relaying the capability of a specific application of effort to produce a specific outcome effectively with a minimum amount or quantity of waste, expense, or unnecessary effort. "Efficiency" has widely varying meanings in different disciplines.
The term "efficient" is very much confused and misused with the term "effective". In general, efficiency is a measurable concept, quantitatively determined by the ratio of output to input. "Effectiveness
", is a relatively vague, non-quantitative concept, mainly concerned with achieving objectives. In several of these cases, efficiency can be expressed as a result as percentage of what ideally could be expected, hence with 100% as ideal case. This does not always apply, not even in all cases where efficiency can be assigned a numerical value, e.g. not for specific impulse.
A slightly broader model of efficiency that nevertheless remains consistent with the "percentage" definition in many cases is to say that efficiency corresponds to the ratio r=P/C of the amount P of some valuable resource produced, per amount C of valuable resources consumed. This may correspond to a percentage if products and consumables are quantified in compatible units, and if consumables are transformed into products via a conservative process. For example, in the analysis of the energy conversion efficiency
of heat engines
in thermodynamics
, the product P may be the amount of useful work output, while the consumable C is the amount of high-temperature heat input. Due to the conservation of energy
, P can never be greater than C, and so the efficiency r is never greater than 100% (and in fact must be even less at finite temperatures).
The term "efficient" is very much confused and misused with the term "effective". In general, efficiency is a measurable concept, quantitatively determined by the ratio of output to input. "Effectiveness
Effectiveness
Effectiveness is the capability of producing a desired result. When something is deemed effective, it means it has an intended or expected outcome, or produces a deep, vivid impression.-Etymology:...
", is a relatively vague, non-quantitative concept, mainly concerned with achieving objectives. In several of these cases, efficiency can be expressed as a result as percentage of what ideally could be expected, hence with 100% as ideal case. This does not always apply, not even in all cases where efficiency can be assigned a numerical value, e.g. not for specific impulse.
A slightly broader model of efficiency that nevertheless remains consistent with the "percentage" definition in many cases is to say that efficiency corresponds to the ratio r=P/C of the amount P of some valuable resource produced, per amount C of valuable resources consumed. This may correspond to a percentage if products and consumables are quantified in compatible units, and if consumables are transformed into products via a conservative process. For example, in the analysis of the energy conversion efficiency
Energy conversion efficiency
Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.-Overview:...
of heat engines
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
in thermodynamics
Thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
, the product P may be the amount of useful work output, while the consumable C is the amount of high-temperature heat input. Due to the conservation of energy
Conservation of energy
The nineteenth century law of conservation of energy is a law of physics. It states that the total amount of energy in an isolated system remains constant over time. The total energy is said to be conserved over time...
, P can never be greater than C, and so the efficiency r is never greater than 100% (and in fact must be even less at finite temperatures).
In physics
- Efficient energy useEfficient energy useEfficient energy use, sometimes simply called energy efficiency, is the goal of efforts to reduce the amount of energy required to provide products and services. For example, insulating a home allows a building to use less heating and cooling energy to achieve and maintain a comfortable temperature...
, useful work per quantity of energy, mechanical advantage over ideal mechanical advantage, often denoted by the Greek lowercase letter η (EtaETAETA , an acronym for Euskadi Ta Askatasuna is an armed Basque nationalist and separatist organization. The group was founded in 1959 and has since evolved from a group promoting traditional Basque culture to a paramilitary group with the goal of gaining independence for the Greater Basque Country...
)- In thermodynamics:
- Energy efficiencyEnergy conversion efficiencyEnergy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.-Overview:...
, measure of second law thermodynamic loss - Thermal efficiencyThermal efficiencyIn thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...
, useful work per the higher heating value of the fuel
- Energy efficiency
- Radiation efficiency, ratio of radiated power to power absorbed at the terminals of an antenna
- Volumetric efficiencyVolumetric efficiencyVolumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio of what quantity of fuel and air actually enters the cylinder during induction to the...
, in internal combustion engine design for the RAF
- In thermodynamics:
- Lift-to-drag ratioLift-to-drag ratioIn aerodynamics, the lift-to-drag ratio, or L/D ratio, is the amount of lift generated by a wing or vehicle, divided by the drag it creates by moving through the air...
- Faraday EfficiencyFaraday efficiencyFaraday efficiency describes the efficiency with which charge are transferred in a system facilitating an electrochemical reaction. The word "faraday" in this term has two interrelated aspects...
, electrolysis - Quantum efficiencyQuantum efficiencyQuantum efficiency is a quantity defined for a photosensitive device such as photographic film or a charge-coupled device as the percentage of photons hitting the photoreactive surface that will produce an electron–hole pair. It is an accurate measurement of the device's electrical sensitivity to...
, a measure of sensitivity of a photosensitive device - Grating efficiency, a generalization of the reflectance of a mirror, extended to a diffraction grating
In economics
- Economic efficiency, a general term, capturing the amount of waste or other undesirable features
- Financial market efficiencyFinancial market efficiencyIn the 1970s Eugene Fama defined an efficient financial market as "one in which prices always fully reflect available information”.The most common type of efficiency referred to in financial markets is the allocative efficiency, or the efficiency of allocating resources.This includes producing the...
, how efficient is the trading going on the financial markets- Pareto efficiencyPareto efficiencyPareto efficiency, or Pareto optimality, is a concept in economics with applications in engineering and social sciences. The term is named after Vilfredo Pareto, an Italian economist who used the concept in his studies of economic efficiency and income distribution.Given an initial allocation of...
, making one individual better off, without making any other individual worse off - Kaldor-Hicks efficiencyKaldor-Hicks efficiencyKaldor–Hicks efficiency, named for Nicholas Kaldor and John Hicks, also known as Kaldor–Hicks criterion, is a measure of economic efficiency that captures some of the intuitive appeal of Pareto efficiency, but has less stringent criteria and is hence applicable to more circumstances...
, like a less stringent Pareto efficiency - Allocative efficiencyAllocative efficiencyAllocative efficiency is a theoretical measure of the benefit or utility derived from a proposed or actual selection in the allocation or allotment of resources....
, an optimal distribution of goods - Efficiency wagesEfficiency wagesIn labor economics, the efficiency wage hypothesis argues that wages, at least in some markets, are determined by more than simply supply and demand. Specifically, it points to the incentive for managers to pay their employees more than the market-clearing wage in order to increase their...
, paying workers more than the market rate for increased productivity
- Pareto efficiency
- Business efficiency, expenses as a percentage of revenue, etc.
- Efficiency MovementEfficiency MovementThe Efficiency Movement was a major movement in the United States, Britain and other industrial nations in the early 20th century that sought to identify and eliminate waste in all areas of the economy and society, and to develop and implement best practices. The concept covered mechanical,...
, of the Progressive Era (1890–1932), advocated efficiency in the economy, society and government
In other sciences
In computing:- Algorithmic efficiencyAlgorithmic efficiencyIn computer science, efficiency is used to describe properties of an algorithm relating to how much of various types of resources it consumes. Algorithmic efficiency can be thought of as analogous to engineering productivity for a repeating or continuous process, where the goal is to reduce...
, optimizing the speed and memory requirements of a computer program - Storage efficiencyStorage EfficiencyStorage efficiency is the ability to store and manage data that consumes the least amount of space with little to no impact on performance; resulting in a lower total operational cost. Efficiency addresses the real-world demands of managing costs, reducing complexity and limiting risk...
, effectiveness of computer data storage - Efficiency factorEfficiency factor-Data communication:In data communications, the ratio of the time to transmit a text automatically at a specified modulation rate to the time actually required to receive the same text at a specified maximum error rate....
, in data communications - Efficiency (statistics)Efficiency (statistics)In statistics, an efficient estimator is an estimator that estimates the quantity of interest in some “best possible” manner. The notion of “best possible” relies upon the choice of a particular loss function — the function which quantifies the relative degree of undesirability of estimation errors...
, a count of desirability of an estimator - Material efficiencyMaterial efficiencyMaterial efficiency is a description or metric which expresses the degree in which usage of raw materials, construction projects or physical processes are used or carried out in a manner which consumes, incorporates, or wastes less of a given material compared to previous measures...
, compares material requirements between construction projects or physical processes - Administrative efficiency, increasing transparency within public authorities and simplification of rules and procedures for citizens and businesses