The length of time that a product or appliance is expected to meet a certain level of performance under nominal operating conditions; in a luminaire, the period after which the lumen depreciation and lamp failure is at 70% of its initial value.

Defects, such as dangling bonds, induced in an amorphous silicon semiconductor upon initial exposure to light.

The inherent characteristic of a material to inhibit the transfer of energy. In electrical conductors, electrical resistance results in the generation of heat. Electrical resistance is measured in Ohms. The heat transfer resistance properties of insulatio ...

The capability of doing work; different forms of energy can be converted to other forms, but the total amount of energy remains the same.

A wall with high thermal mass used to store solar energy passively in a solar home. The wall absorbs solar energy and transfers it to the space behind the wall by means of radiation and by convection currents moving through spaces under, in front of, and ...

For a wind turbine, the ratio of the speed of the tip of a turbine blade for which the power coefficient is at maximum.

A ratio of the work or useful energy output of a system versus the amount of work or energy inputted into the system as determined by using the same energy equivalents for energy in and out. Is used as a measure of the steady state performance or energy e ...

An apparatus for measuring force or power, especially the power developed by a motor.

A region of electrical contact between two different materials.

The load-carrying ability of an electric power plant during a specific time interval and period when related to the characteristics of the load to be/being supplied; determined by capability, operating power factor, and the portion of the load the station ...

A measure of window glazing performance that is the ratio of the total solar heat gain through a specific window to the total solar heat gain through a single sheet of double-strength glass under the same set of conditions; expressed as a number between 0 ...

A type of passive solar heating system where heat is collected in one area for use in another.

An electromagnetic device that changes the voltage of alternating current electricity. It consists of an induction coil having a primary and secondary winding and a closed iron core.

This represents three layers of glazing in a window with an airspace between the middle glass and the exterior and interior panes.

An architectural feature used to shade exterior walls; usually made of a lattice of metal or wood; often covered by vines to provide additional summertime shading.

The structural materials and elements used to construct a wall.

The voltage developed across a cell by the current flow through the resistance of the cell.

An electric motor rated at less than one horse power (hp).

A term used for lighting appliances; the ratio of lumens received on a flat surface to the light output, in lumens, from a lamp; used to evaluate the effectiveness of luminaries in delivering light.

A company that specializes in undertaking energy efficiency measures under a contractual arrangement whereby the ESCo shares the value of energy savings with their customer.