ENERGY / UTILITY GLOSSARY
speed drive (ASD) - An electronic device that controls the rotational
speed of a piece of motor-driven
equipment (e.g., a compressor, fan, or pump). Speed control is obtained by
adjusting the frequency of the
voltage applied to the motor. This approach usually saves energy for
Association of Energy Engineers, professional society of the energy industry.
AEE provides testing and
certification of energy engineers in several technical areas.
(AHU) - An equipment package that includes a fan or blower, heating
and/or cooling coils,
air filtration, etc. for providing heating, ventilation, and air conditioning
(HVAC) to a building. Usually roof-top mounted
and sometimes abbreviated as a RTU. A candidate for efficiency
improvement through control improvement, variable
speed drive, leakage reduction, etc.
ASHRAE - Acronym for American
Society of Heating, Refrigerating and Air-Conditioning Engineers.
sequencer - A control system that operates compressors in sequence
according to rules usually
developed to improve overall system efficiency.
- A device that provides starting voltage and limits the current during
normal operation for electrical
discharge lamps such as fluorescent lamps.
factor (BF) - The percentage of rated lamp lumens that will be
produced by the specific lamp/ballast combination.
Building Automation System
method - A method of predicting heating and/or cooling loads by doing
load calculation at different outdoor
temperatures and then multiplying the result by the number of hours of
occurrence of each temperature.
- The removal of water from an evaporative system (e.g., cooling
tower or boiler) to reduce mineral
concentration that can cause scaling.
horsepower - A rate of steam production equal to the evaporation of
34.5 pounds of water per hour at
a temperature of 212°F
into dry steam at 212°F.
One boiler horsepower is equal to 33,475 Btu per
hour of steam production.
horsepower (bhp) - Horsepower required at the blower, compressor,
fan, or pump shaft to
perform actual work. Often less than the electric motor nameplate rating, but
British thermal unit (Btu) -
A unit of heat energy approximately equal to the quantity of heat required to
raise one pound of water by 1°F.
CEM - Certified Energy
Manager, international professional designation available through training and
by the Association of Energy Engineers (AEE)
CFC (chlorofluorocarbon) - A
family of chemicals used as refrigerants that is being tightly regulated
and phased out of production due to stratospheric ozone depletion potential.
Examples: R-11, R-12, R-113,
of Performance (COP) - A
measure of refrigeration efficiency. The ratio of the rate of heat removed
(cooling effect) to the rate of heat input required, expressed in the same
(COGEN)- The generation of electricity and
the concurrent use of rejected thermal energy as
an auxiliary energy source (e.g., for heating or absorption cooling).
Also known as Combined Heat & Power (CHP)
(CRI) - The effect of a light source on color on a scale of 1 to 100
where 100 represents
no color distortion. Lower CRI ratings produce more
COMMODITY - The actual energy provided by a regulated or unregulated
utility. For natural gas it is the natural gas
without LDC delivery charges. For electricity it is the 'generation" component
of the bill .. without EDC charges for
delivery and service.
compensation - A photocell-controlled dimming system that reduces
lamp output when daylight is present.
DDC - Direct Digital
Control, description of control method of some BAS / EMS systems
block rate - An electric supply rate structure in which the unit
price of electricity decreases as the
amount of electricity used increases. Savings for energy conservation occurs at
the lowest (or "incremental"
or "marginal") rate, not the average rate.
MANAGEMENT- Major element of Energy Management dealing with energy
and control. Demand-Side EM deals with all cost savings opportunities inside
of the building.
Management (DSM) - The process of
managing the consumption of electrical energy,
generally to minimize demand and costs.
EDC - Electric Distribution
Company, your local regulated electric utility company
Electricity : I = AMPs, E =
Voltage , KW = Kilowatts (real power), PF = Power Factor
Conservation Measure (ECM)
- An energy audit recommendation.
Energy Management System, computerized system for fully
automatic control of HVAC, lighting,
refrigeration, etc. for temperature management, comfort and energy savings.
Contract (ESPC) - A
way to finance and implement a capital improvement
project by using utility cost savings to cover project costs. This service is
provided by an energy services
company (ESCO). The Federal Government has an accelerated
ESPC called Super ESPC
Services Company (ESCO)
- A company that
offers to reduce a client's utility costs, often with the cost
savings being split with the client through an energy performance contract (EPC)
or a shared-savings agreement.
Heat Pump - A
heat pump that uses the ground, ground water, or pond water as a heat source or
heat sink, rather than using outside air. Ground or water temperatures are more
stable and are warmer in winter
and cooler in summer than air temperatures. Geothermal heat pumps can operate
more efficiently than other
types of heat pumps.
- The amount of dissolved calcium salts and/or magnesium present in
water. Hardness is measured
in units of parts per million (ppm) or grains per gallon (gpg). [gpg x 17.1 =
ppm] Poor water treatment can
result in excessive scale that provides excessive resistance to heat transfer
and thus inefficiency and higher costs.
pipe - A device that transfers heat by the evaporation and
condensation of an internal fluid.
recovery ventilator - A device that captures heat from exhaust air
from a building and transfers it to
the fresh air entering the building to preheat the air and thus reduce energy
consumption and cost.
(HID) - A generic term used to describe metal halide, sodium, and mercury
(HP) - (Electrical/mechanical horsepower,
not boiler horsepower.) A shaft energy output rate of
550 foot-pounds per second, usually specified for electric motors as the maximum
output. One electrical HP is
equal to 0.7457 kW or 2,545 Btu/hour. The actual kW required will be higher due
to motor inefficiency.
Hours Use - electric utility
calculation, normally used outside of electricity tarriffs, determined by
monthly kWh (consumption) by Kw (demand peak), resulting in 'hours' use
HVAC systems - Heating,
ventilation, and air conditioning systems. Common systems
capable of providing
tremendous amounts of comfort and tremendous amounts of waste, sometimes
simultaneously. Variation of
this term is HVACR (with Refrigeration included)
IESNA - Illuminating
Engineering Society of North America.
- true cost of purchasing an additional energy unit or saving energy
based on the last
step in a electricity or natural gas tarriff ( based on volume of consumption
during a monthly billing period).
The incremental value of an energy unit is often lower than the 'average' cost
per energy unit.
service - Utility service (electric or natural gas) supplied under
agreements that allow the supplier
to curtail or stop service at times in return for a discounted rate at other
(kW) - A unit of electric power or capacity equal to 1,000 watts.
“Demand” or “capacity” charges for
electricity are usually based on the peak kW occurring during the billing
period, often only as measured during
times defined as “on peak” hours. KW peaks are normally
measured every 15 or 30 minutes. The highest KW
period during the month sets KW demand peak billed for the entire month. Some
rates index KWH consumption
rates based on the KW demand peak ( Rate tariffs used the term KWH per KW)
(kWh) - A unit of electric energy consumption equal to that consumed
in using a power level
of one kilowatt (1,000 watts) for a duration of one hour. Example:
Illuminating ten 100-watt bulbs for one
hour consumes 1 kWh. 1 KWh = 3,413 BTU.
Local Distribution Company - Your local regulated
natural gas utility company
factor - The average percentage of capacity of a utility that is
used over a given period of time such as
a month or year. Deregulated electricity sellers prefer clients with high load
factors (i.e., stable and predictable
loads) and sometimes offer them preferred rates.
coating (for windows) - A coating applied to the surface of window
glazing to reduce heat transfer
through the glazing by reducing
Lumen - A measurement of
light . The official definition of the
lumen, the unit of luminous flux, is:
The luminous flux dF of a source of
luminous intensity I (cd)
in an element of solid angle dR is given by
dF = IdR In plain English: The flux from a light
source is equal to the intensity in candela multiplied
by the solid angle over which the light is emitted,
taking account of the varying intensity in different directions.
Lumens Per Watt
- Method to compare the energy efficiency of various types of
lighting. Higher lumens per
watt indicates more light for less KWH consumption.
Luminaire - A complete lighting unit consisting of lamp(s),
lamp protector(s), ballast(s), and components
to direct and control the light.
Rate - The rate that has to be paid for the
last increment of service. For example, with a declining block
electric rate, the marginal rate is the rate in the last rate block used and is
lower than the average rate.
Savings from reducing consumption will occur at the marginal rate, not the
1,000 cubic feet of natural gas, having an energy value of
approximately one million Btu.
and Verification ( M&V
) - A process capable of keeping an Energy
Contract fair to all parties.
National Electrical Code
Sensor - A control device that senses the
presence of a person in a given space and is commonly
used to control lighting. Occupancy sensors are sometimes used to control
HVAC in some building types.
- Fresh air taken from
outside that has not previously circulated through the HVAC system.
air often requires substantial heating and air conditioning and should be
- The time rate of doing work or consuming energy, usually measured
in Btu/hour, horsepower, or kW.
Power use is often billed in addition to energy use (e.g., an electric bill will
have both kW and kWh charges).
Factor (PF) -
The ratio of power
actually being used in an electric circuit, expressed in kW, to the
power that is apparently being drawn from the power source, expressed in
In other words,
the ratio of "active" or "real" power (that
actually turns the motor shaft) to "apparent power." The apparent power
includes "reactive power" strictly used to develop the magnetic field. Reactive
power creates no useful work,
results when current is not in phase with voltage, and can be corrected using
capacitors or other devices.
- A measure of thermal resistance used to compare insulating values. The
higher the R-value number
of a material, the better its insulating properties and the slower the heat
flows through it.
Power - Electrical power strictly used to
develop magnetic field. Reactive power is never converted to
useful power such as shaft power, but it often gets billed anyway. Power factor
correction can reduce
reactive power costs. See "power factor."
Pricing (RTP) -
The instantaneous pricing of
electricity based on the cost of the electricity at the
time it is used by the customer. RTP rates can vary over a wide range and are
typically very high when system
demand is high (e.g., on a hot, summer, weekday afternoon). Real-time rates
differ from time-of-use (TOU) rates
in that they are based on actual (rather than forecasted) prices that may
fluctuate frequently during a day and
are weather-sensitive rather than varying with a set schedule.
Tax Exemption -
An opportunity to reduce utility costs that is available to manufacturers and
in many states. Regulations vary by State.
Agreement - An agreement to share utility
cost savings in return for providing the studies, designs,
systems, and/or support necessary to create the savings. Or, sometimes, an
agreement to surrender more than
a fair share of the actual savings to an outside firm that does the calculations
and inflates the savings estimates.
Contract - A contract that provides utility
service under terms and conditions other than those listed
in the utility tariff. For example, an electric utility may enter into a special
contract with a large customer
to provide electricity at a lower-than-tariff rate in order to prevent the
customer from taking advantage of other
options (e.g., deregulated competition or on-site cogeneration) that would
result in the loss of the customer's load.
SUPPLY-SIDE ENERGY MANAGEMENT - Major element of Energy Management
dealing with the cost of the energy
based on regulated tariffs or the cost of the 'commodity' in deregulated States.
Supply-Side EM deals with the utility
meter and everything outside of the building.
- Industry nomenclature for a fluorescent lamp that is 8 one-eighths of an
inch in diameter
(i.e., one inch diameter). A T12 lamp is 12 one-eighths or 1.5 inches in
- 100,000 Btu. A common unit for quantifying the energy content of
natural gas delivery.
1 therm = 100 CF or .1 MCF
(TOU) rate - Pricing of electricity based on several time blocks per
(e.g., on-peak, mid-peak, off-peak, etc.) and on seasons of the year (e.g.,
summer and winter).
Not the same as real-time pricing (RTP). See " real-time pricing (RTP)."
Also called Time-of-Day demand metering.
of Refrigeration - 12,000 Btu/hour of
cooling capacity. One
ton of capacity is equal to the heat required to
melt 2,000 pounds of ice in 24 hours.
(or U-value) - A
measure of how well heat is transferred by a window, thus affecting heating and
conditioning costs. U-factor is the inverse of R-value. The lower the U-factor,
the better the window will
retain heat on a cold day or cooling on a hot day.
Speed Drive (VSD)
- An electronic device that controls the rotational speed of a piece of
Frequency Drive (VFD)
equipment (e.g., a blower, compressor, fan, or pump). Speed control is obtained
by adjusting the frequency
of the voltage applied to the motor. This approach usually saves energy for
Also known as
VAV System (Variable
- An HVAC system serving multiple zones that controls the
temperature in each zone by controlling the amount of heated or cooled air
supplied to the zone.