The Energy Catalyzer (also called E-Cat) is a claimed cold fusion reactor.

An energy carrier is a substance (fuel) or sometimes a phenomenon (energy system) that contains energy that can be later converted to other forms such as mechanical work or heat or to operate chemical or physical processes.

Energy bars (candy bars) are supplemental bars containing cereals and other high energy foods targeted at people who require quick energy but do not have time for a meal.

An energy audit is an inspection survey and an analysis of energy flows for energy conservation in a building.

Nanotechnology, a relatively new field of science and engineering, has shown promise to have a significant impact on the energy industry.

An energy amplifier is a novel type of nuclear power reactor, a subcritical reactor, in which an energetic particle beam is used to stimulate a reaction, which in turn releases enough energy to power the particle accelerator and leave an energy profit for power generation.

Energy aggregation is when entities partner together to buy energy from developers, at smaller volumes while retaining the economic advantages of a high-volume purchase.

Energy accounting is a system used to measure, analyze and report the energy consumption of different activities on a regular basis. This is done to improve energy efficiency, and to monitor the environment impact of energy consumption.

Energy resources bring with them great social and economic promise, providing financial growth for communities and energy services for local economies.

In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.

An endothermic process is any process with an increase in the enthalpy H (or internal energy U) of the system.

An encoder is a sensor which turns a position into an electronic signal.

An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation.

Empirical research is research using empirical evidence.

Empirical evidence is the information received by means of the senses, particularly by observation and documentation of patterns and behavior through experimentation.

The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation.

Emissions trading (also known as cap and trade, emissions trading scheme or ETS) is a market-based approach to controlling pollution by providing economic incentives for reducing the emissions of pollutants.

Process to reduce emissions on existing power plants or machinery or a plan for new designs.

An emissions target or greenhouse gas emissions reduction target is the central policy instrument of international greenhouse gas emissions reduction politics and a key pillar of climate policy.

A ratio of power plant emissions per megawatts of electricity (MWe) that are produced.