Central Air-Conditioning: In the detailed tables, a category including households that use both room/wall airconditioners and central air-conditioning. (See Air-Conditioning Equipment.)

Central City: Usually one or more legally incorporated cities within the Metropolitan Statistical Area (MSA) that is significantly large by itself or large relative to the largest city in the MSA. Additional criteria for being classified "central city" include having at least 75 jobs for each 100 employed residents and having at least 40 percent of the resident workers employed within the city limits. Every MSA has at least one central city, which is usually the largest city. Central cities are commonly regarded as relatively large communities with a denser population and a higher concentration of economic activities than the outlying or suburban areas of the MSA. Suburban are those parts of the MSA that are not designated as central city. In this report, the central city and suburban areas are called urban; in previous RECS reports, these components were referred to as metropolitan areas. (See Metropolitan Statistical Area, Suburban, and Urban.)

Central Warm-Air Furnace: A type of space-heating equipment where a central combustor or resistance unit generally using natural gas, fuel oil, or electricity, providing warm air through ducts leading to the various rooms. Heat pumps are not included in this category. A forced-air furnace is one in which a fan forces air through the ducts. In a gravity furnace, air is circulated by gravity relying on the natural flow of warm air up and cold air down; the warm air rises through ducts and the cold air falls through ducts that return it to the furnace to be reheated, thus completing the circulation cycle.

City: A classification based on respondent's judgment. (See Urban/Rural Location.)

Climate Zone: One of five climatically distinct areas, defined by long-term weather conditions affecting the heating and cooling loads in buildings. The zones were developed by the Energy Consumption Division from seven distinct climate categories originally identified by the American Institute of Architects (AIA) for the U.S. Department of Energy

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and the U.S. Department of Housing and Urban Development. The zones were determined according to the 30-year average (1951-1980) of the annual heating and cooling degree-days (base 65 degrees Fahrenheit). The zones are defined as follows:

An individual household was assigned to a climate zone according to the 30-year average annual degree-days for an appropriate nearby weather station. (See Cooling Degree-Days [CDD] ) and Heating Degree-Days [HDD].)

Clothes Dryer: An appliance that dries laundry through the application of heat and rapid air movement. The hot air used is typically heated by electricity or gas (either natural gas or LPG).

Clothes Washer: An appliance for automatically cleaning home laundry. It has an opening on its top or its front offering access to the washer tub. An agitator, located within the tub, moves the articles to be cleaned through the wash water. The machine is powered by an electric motor connected to the tub and agitator via a transmission, clutches, and linkages. In front-loading machines, the articles are moved by a rotating tube rather than an agitator.

Coal: A combustible mineral substance (carbonized vegetable matter). In this report, the term includes its derivative, coke, which is formed by destructive distillation or imperfect combustion. Data on the use of coal were collected but consumption and expenditure data were not collected.

Conditional End-Use Intensity (CEUI): A measure of how intensely energy is used that allows comparisons across housing units and households by adjusting either the end-use consumption or expenditures for the effects of certain characteristics, such as floorspace, degree-days, or household members for households that use an energy source for a particular end use. In the case of space-heating intensity, only the heated floorspace and heating degree-days are used. The air-conditioning intensity uses only the cooled floorspace and cooling degree-days. The water-heating intensity adjusts consumption and expenditures for the effects of the number of household members on water-heating consumption.

Conditional Energy Intensity: A measure of how intensely energy is used that allows comparisons across housing units and households by adjusting either energy consumption or expenditures for the effects of certain characteristics, such as weather, size of unit, and number of household members for households that use a particular energy source. (See Conditional End-Use Intensity and Intensity.)

Condo Fee: In condominiums, the fee paid to the homeowners' association for maintenance, management, insurance, and, in some cases, utilities.

Condominium: An apartment or house owned in a project of similar units. The owner has his/her own deed and, most likely, his/her mortgage on the unit. The owner also holds a common or joint ownership on all common areas, such as hallways, entrances, and elevators. Ownership may cover single-family houses, including row houses and townhouses, as well as apartments.

Consumption: The amount of electricity or natural gas used by, or delivered to, a household during a 365-day period. For fuel oil, kerosene, and LPG, the quantity represents fuel purchased, not fuel consumed. If the level of fuel in the tank was the same at the beginning and end of the annual period, then the quantity consumed would be the same as the quantity purchased. Measurements or reports of the actual level of fuel in the tank were not included in the RECS data collection.

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Control Total: The number of elements in the population or a subset of the population. The sample weights for the

observed elements in a survey are adjusted so that they add up to the control total. The value of a control total is not obtained from the survey; it is obtained from an outside source. In this report, the control totals are obtained from the Current Population Survey. (See Appendix A, "How the Survey was Conducted.”)

Conversion Factors: See Btu Conversion Factors and Metric Conversion Factors.

Cooking Stove: A stove built for preparing food. In this survey, it may be used as the main heating equipment. (See Heating Equipment.)

Cooling Degree-Days (CDD): A measure of how hot a location was over a period of time, relative to a base temperature. In this report, the base temperature is 65 degrees Fahrenheit, and the period of time is one year. The cooling degree-days for a single day is the difference between that day's average temperature and the base temperature if the daily average is greater than the base; it is zero if the daily average temperature is less than or equal to the base temperature. The number of cooling degree-days for a longer period of time is the sum of the daily cooling degree-days for the days in that period. Annual cooling degrees-days averaged over 30 years from 1961 to 1990 are called Normal Cooling Degree-days. Cooling degree-days can also be calculated by using a base temperature other than 65 degrees. The computation is performed in an analogous manner. (See Climate Zone.)

Cord of Wood: An amount of wood measuring 4 feet by 4 feet by 8 feet, or 128 cubic feet.

Crawl Space: Space between the ground and the floor of a house in which a person cannot walk upright. An enclosed crawl space is one not accessible from the outside of the house (except by a door or window) because the walls of the crawl space protect it from the weather. A crawl space "open to the outside" is accessible from outside the house, even though it may be covered by a trellis or lathwork or some kind of brickwork that leaves space for circulation of air.

Cubic Foot (cf): As a natural gas measure, the volume of gas contained in a cube with an edge that is 1 foot long at standard temperature and pressure (60 degrees Fahrenheit and 14.73 pounds standard per square inch). (See Btu Conversion Factors and Natural Gas.)

Current Dollars: Unless otherwise noted, all dollar values presented in this report are expressed in the current dollars at the time of data collection. The dollar amounts are not directly comparable across time periods since they have not been adjusted for the effects of inflation. In contrast, real dollars are current dollars that have been adjusted for the effects of inflation.

Dishwasher: A built-in or portable appliance used for automatically cleaning dishware, utensils, and cutlery. The national appliance efficiency standards required that, by 1988, dishwashers be equipped with an option to dry without heat.

Electric Air-Conditioning Intensity: In this report, the ratio of end-use electric air-conditioning consumption or expenditures to square footage of cooled floorspace and cooling degree-days (CDD) (base 65 degrees Fahrenheit). Only the CDD and square feet for households that have air-conditioning equipment are included in the ratio. The intensity provides a way of comparing different types of housing units and households by controlling for differences in housing unit size and weather conditions. The square footage of cooled floorspace is equal to the product of the total square footage times the ratio of the number of rooms that are cooled to the total number of rooms. If the entire housing unit is cooled, the cooled floorspace is the same as the total floorspace. The ratio is calculated on a weighted, aggregate basis.

Electric Pump for Well Water: A pump that forces the water from a well below ground level up into the water pipes that circulate through the house. When this pump is not working, there is a limited supply of running water in the house.

Electricity: Metered electric power delivered by a central utility company to a residence via power lines. Because there are no volumetric measures of electricity as with the fossil fuels, electricity is measured as the amount of power used at any instant (demand expressed in watts (W) or kilowatts (kW)) or as power used over a given time (consumption expressed in kWh). The heat equivalent for electricity is 3,412 Btu per kWh, but this is a derived form of energy and

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does not represent the amount of energy needed to generate the electricity and transmit it to the building. Generation and transmission requires about 3 times 3,412 Btu per kWh, or 11,620 Btu per kWh. Energy is used in preparing other fuels for consumption from their condition as mined and delivering them to a site for use, but these amounts of energy are relatively small compared to the Btu value of the fuel consumed. (See Primary Electricity and Btu Conversion Factors.)

Electricity Paid by Household: The household paid the electric utility company directly for all household uses of electricity (such as water heating, space heating, air-conditioning, cooking, lighting, and operating appliances.) Bills paid by a third party are not counted as paid by the household.

Eligible for Federal Assistance: Households are categorized as eligible for Federal energy assistance if their income is below the Federal standard. The Federal standard is 150 percent of the poverty line or 60 percent of statewide median income, whichever is the higher income. Individual States can set the standard at a lower level than the Federal one. (See Poverty Line.)

End Use: A function for which fuels (energy sources) are used in the household. Five major energy end-use categories were estimated: space heating, air-conditioning, water heating, refrigerators, and appliances. The amount of energy used for these end uses is estimated by means of a nonlinear regression technique, rather than by data that are actually measured. (See Space Heating, Air-Conditioning, Water Heating, Refrigerators, and Appliances.)

Energy Source: A type of energy or fuel used by the household. Electricity is included as a fuel. The energy sources identified for this report are electricity, natural gas, fuel oil, kerosene, liquefied petroleum gas (propane), wood, coal, and solar. The major fuels are electricity, natural gas, fuel oil, kerosene, and liquefied petroleum gas (LPG). (See Electricity, Natural Gas, Fuel Oil, Kerosene, Liquefied Petroleum Gas, Wood, Coal, and Solar Energy.)

Energy Supplier: A company that provides electricity, natural gas, fuel oil, kerosene, or LPG to the household. (See Authorization Form and Appendix A, "How the Survey Was Conducted.")

Estimated Bill: A set of charges for a fuel, calculated by the supplier when the meter is not read. The estimate may be based on one or more of the following factors: past usage, usage by similar households, and weather data.

Evaporative Cooler (Swamp Cooler): A type of cooling equipment using the evaporation of water to cool air. This type of equipment is commonly found in warm, dry climates. Evaporative cooling units do not cool air by use of a refrigeration unit, so for this report they are not considered air-conditioning equipment, and are listed with appliances.

Expenditures: Money spent for the energy used in, or delivered to, a housing unit during a given period of time. For this report, all expenditure statistics are presented on an annual basis for calendar year 1997. The total dollar amount includes State and local taxes but excludes merchandise, repairs, or special service charges. Electricity and natural gas expenditures are for the amount of those energy sources consumed. Fuel oil, kerosene, and LPG expenditures are for the amount of fuel purchased, which may differ from the amount of fuel consumed. For households that do not pay their fuel supplier directly, the expenditures for fuels are estimated and included in the tables. (See Consumption.)

Expenditures as a Percentage of Income: The annual household energy expenditures divided by the household's annual income. The median percentage of income is the percentage spent on energy for the household, for the middle income value in the population when the households are ranked by the percentage they spend on energy. That is, 50 percent of the weighted households in the cell spend a lower percentage on energy than the median value. Facsimile Machine (FAX): Equipment that transmits and receives printed material over telephone lines. Fireplace: Usually a masonry unit which burns wood, is built into the wall of a house and has a permanent chimney. Fireplaces in mobile homes are included. Fireplaces may have glass doors or metal shields to cover the opening into the room. Included are fireplaces that use equipment fueled by natural gas or LPG. These gas fireplaces may or may not have a flue to the outside. Accessories, such as convective grates or radiant grates, may be present to increase the efficiency of the fireplace. A free-standing fireplace that can be detached from its chimney is a heating stove.

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Floor, Wall, or Pipeless Furnace: Space-heating equipment consisting of a ductless combustor or resistance unit, having an enclosed chamber where fuel is burned or where electrical-resistance heat is generated to warm the rooms of a building. A floor furnace is located below the floor and delivers heated air to the room immediately above or (if under a partition) to the room on each side. A wall furnace is installed in a partition or in an outside wall and delivers heated air to the rooms on one or both sides of the wall. A pipeless furnace is installed in a basement and delivers heated air through a large register in the floor of the room or hallway immediately above.