(CEC) denotes glossary definitions excerpted from the California Energy Commission Enhanced Automation Technical Options Guidebook.1 (EPA) denotes glossary definitions excerpted from the US EPA Energy Star® Building Upgrade Manual.2

Accent lighting Lighting that draws attention to special features or enhances the aesthetic qualities of an indoor or outdoor environment, such as lobbies and conference rooms.

Air economizer A component of an HVAC system that provides cooling without the use of mechanical refrigeration or air-conditioning. An economizer saves energy by regulating dampers when the outdoor air temperature and ambient conditions are sufficient to provide the heating and cooling needs of the building interior. (CEC)

Ambient lighting Provides general base-level illumination of space. Ballast: Electrical or magnetic devices that provide appropriate voltage when a fluorescent light is turned on and limit and stabilize the amount of current flowing to the lamp during operation. Fluorescent lights require ballasts to operate.

BAS See Building automation system.

BMS See Building management system.

Boiler Pressure vessel designed to transfer heat produced by combustion or electric resistance to a fluid. In most boilers, the fluid is water in the form of liquid or steam. (EPA)

British thermal unit (BTU) Unit of energy used commonly for heating and airconditioning. BTU/hour (BTU/hr) is also used to describe the power of heating and cooling systems. A BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

BTU See British thermal unit.

Building automation system (BAS) A system of automated controls for a range of building systems. Building automation systems range in degree of complexity, but are typically less sophisticated than energy management systems (EMS). May also be referred to as a building management system (BMS).

Building envelope The outer shell of a building, including walls, roof, windows and doors. (EPA)

Building management system (BMS) See Building automation system.

CFL See Compact fluorescent lamp.

Chiller Mechanical device that generates cold liquid, which is circulated through cooling coils to cool the air supplied to a building. (EPA)

Circuit level (energy monitoring) Electricity monitoring performed during an energy audit where electricity flow through each circuit is measured individually. Circuit level monitoring allows for a precise analysis of the specific electricity draw by different systems within a building.

Commissioning A process by which equipment is tested to make sure it is performing according to design intent. Commissioning should be performed periodically on HVAC and lighting systems.

Compact fluorescent lamp (CFL) Fluorescent lamps suitable for using in fixtures designed for standard incandescent bulbs, with longer life and lower energy usage than comparable incandescent bulbs.

Cooling capacity An HVAC performance measure rated as the amount of heat energy a cooling unit can remove from a space per hour, expressed in BTU per hour.

Demand response The application of available load and price response mechanisms to balance energy demand and supply.

Demand The rate at which energy is delivered to loads and scheduling locations by generation, transmission or distribution facilities. For a utility, it is the level at which electricity or gas is delivered to users at a point in time.

Demand charges Fees levied by a utility for electric demand. Demand charges are set based on a customer’s peak demand. (EPA)

Diffuser (lighting) A device that distributes light produced by lamps into a space. (EPA)

Dimmer (lighting) A device that varies the voltage running to a lamp in order to reduce or increase lighting intensity.

Direct meter A utility payment configuration in which a tenant contracts with and is billed by the utility.

Discount rate Rate used to calculate the present value of future cash flows.

EER See Energy efficiency ratio.

Efficacy The ratio of lamp lumen output to total lamp power input expressed in lumens per watt. (EPA)

EIS See Energy information system.

Energy efficiency ratio (EER) Cooling capacity (BTU/hour) divided by the total input power (watts) requirement. (EPA)

Energy information system (EIS) A platform that communicates with external and internal signals of a building, such as electricity prices, weather and power quality. An EIS can also provide a gateway to the energy management system as well as analyses of various levels of data. (CEC)

Fixtures Light fixture or luminaire is an electrical device used to create artificial light or illumination.

Footcandle Unit of illuminance equal to one lumen per square foot. (EPA)

HID See High-intensity discharge.

High-intensity discharge (HID) A generic term for mercury vapor, metal halide and high-pressure sodium lamps and fixtures. Similar in design to an incandescent bulb, but instead of a filament, current is passed through a capsule of gas.

Hurdle rate Minimum acceptable rate of return on a project.

HVAC Stands for Heating, Ventilation and Air-Conditioning.

IRR See Internal rate of return.

Incandescent lamp One of the oldest electric lighting technologies available. Incandescent bulbs produce light by passing a current through a filament, causing it to become hot and glow (also causing waste heat).

Information technology Term used to describe computing equipment and services. Servers, desktop computers, printers, phones and software are all considered IT.

Internal rate of return (IRR) Discount rate at which investment has zero present value.

IRR See internal rate of return.

IT See Information technology.

Kilowatt (KW) 1,000 watts, a measure of power, similar to horsepower. Power plant capacity is measured in watts.

Kilowatt-hour (KWh) The amount of energy equivalent to a power of one kilowatt running for one hour. Electricity use for a building or a home is measured in KWh.

KW See Kilowatt.

KWh See Kilowatt-hour.

LED See Light emitting diode.

Lens (lighting) Cover for a light fixture; acts as a diffuser.

Light emitting diode (LED) A solid-state light source that delivers a direct beam of light at a very low wattage.

Load The amount of electric power supplied to meet one or more end user’s requirements. May also refer to an end-use devise or end-use customer that consumes power. Related terms: load curtailment.

LPW See Lumens per watt.

Lumens The unit of luminous flux, a measure of the perceived power of light. A standard 100-watt incandescent light bulb emits approx. 1,700 lumens in North America.

Lumens per watt (LPW) A measure of lighting efficiency calculated by dividing the number of lumens produced by the number of watts used.

Luminaire Complete lighting unit, consisting of one or more lamps together with a housing, the optical components to distribute the light from the lamps and the electrical components (ballast, starters, etc.) necessary to operate the lamps. (EPA)

Megawatt-hour (MWh) Unit of energy measurement equal to 1,000 kilowatt-hours (kWh).

MWh See Megawatt-hour.

NPV See Net present value.

Net present value (NPV) A project’s net contribution to wealth: present value minus initial investment.

Off-peak Refers to time during a particular period when electrical demand is relatively low. If a utility uses time-of-day pricing, electric prices will be highest during periods of peak load.

Payback The length of time required for the net revenues of an investment to return the cost of the investment.

Peak demand See Peak load.

Peak load Also known as peak demand. Refers to the highest electrical demand during a particular time period. If a utility uses time-of-day pricing, electric prices will be highest during periods of peak load.

Photosensor A device that responds electrically to the presence of light. (EPA)

Plenum An open space used to distribute cold air or collect hot air (as opposed to ducts). Data centers typically use underfloor plenums to supply air to server aisles.

Power utilization effectiveness Ratio of total data center power consumption to server power consumption. A measure of data center system efficiency.

PUE See Power utilization effectiveness.

Reflector A device installed in luminaires used to direct light from a source via specular or diffuse reflection. (EPA)

Rent inclusion A utility payment configuration in which payment for a service is bundled in with rent, usually as a fixed amount per square foot.

Standby losses A measure of efficiency of commercial water heaters that is a measure of the percentage of heat lost per hour once water is heated. Standby loss is expressed as a percentage, typically ranging from 0.5-2.0% (the lower the value, the more efficient the heater).

Sub-meter A utility payment configuration in which a tenant pays the landlord based on the meter as well as a “handling fee” that will vary based on negotiations, but is typically not more than 12%.

T12 A linear fluorescent lamp with a diameter of 12/8th of an inch.

T5 A linear fluorescent lamp with a diameter of 5/8th of an inch.

T8 A linear fluorescent lamp with a diameter of 8/8th of an inch.

Task lighting Facilitates particular tasks that require more light than is needed for general illumination, for example, desk lamps.

Tax shield The reduction in income taxes that results from taking an allowable deduction from taxable income.

Therm Unit of energy equal to 100,000 BTU.

Thermal efficiency percentage A measure of efficiency of commercial water heaters that represents the percentage of energy from the fuel or electric heating element that is transferred to the water being heated (ranges from 0–100%; the higher the value, the more efficient the heater).

Three-phase A wiring system suitable for installations involving large motors. The system consists of three hot wires and one ground wire.

Tungsten halogen An updated version of a traditional incandescent bulb. It contains halogen gas and uses a tungsten filament.

Uninterruptible power supply Technology designed to ensure that power does not cut out unexpectedly in a data center, resulting in server failure. UPS systems commonly use batteries to back up the electric power supply.

UPS See Uninterruptible power supply.

Virtualization Consolidation of multiple copies of an operating system onto a single server. The operating systems can run simultaneously, dramatically increasing the utilization of the server.

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