FIT
Feed-in Tariff: subsidy paid to for the installation of uneconomic energy supply equipment, notably solar photovoltaic panels, and funded by a levy on predominantly non-domestic users

Flash steam
Steam produced when water (usually condensate) at temperatures exceeding 100ºC is reduced in pressure

Flow metering
Read article...

Fluorescent lamp
Light source consisting of a glass tube, filled with an inert gas and internally coated with fluorescent material which emits light when energised by an electric arc struck in the gas. Click here for a discussion of why it is not more efficient to keep such a lamp turned on when it is not required.

Freezers, efficiency
Click here for discussion of the myth that a full freezer is more efficient

Furnaces
Equipment either electric or fuel-fired for treatment of materials at high temperature. Read article