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Changes in the Types of Residential Heating Equipment

Over the 1978-1997 period, warm-air furnaces have been the most frequently used type of main central heating system in U.S. housing units, followed by steam/hot water systems and heat pumps (Figure 3.8).

(Climate Zones are climatically distinct geographic areas determined according to the 30-year average (1961-1990) of annual heating and cooling degree-days. Heating and cooling degree-days are a measure of how cold or how hot a location is over a one-year period, relative to a base temperature of 65 degrees F. See Appendix E for a detailed map of the areas of the United States included in each climate zone and the precise definition of each climate zone.)

Figure 3.8. Predominate Main Central Heating Systems in U.S. Housing Units, 1978, 1987, and 1997

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Only 1 percent of the steam/hot water systems were located in housing units built in the 1990's; of these none were located in the two most southern climate zones (CZ 4 and CZ 5) that include the States in the Deep South, most of California, and parts of Arizona and New Mexico. A majority, 57 percent of the systems, were in housing units built before 1950, virtually all of which were located in the three most northern climate zones (CZ 1, CZ 2, and CZ 3), which include most of the northern two-thirds of the United States.

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15.9 13.5 13.4

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Heat Pump

Heating Equipment

* The difference between the 1978 and 1997 estimates is statistically significant at the 95-percent confidence level,

Sources: Energy Intormation Administration; 1978, 1987, and 1997 Residential Energy Consumption Surveys.

Figure 3.9. Steam/Hot Water Systems by Year of Construction and Climate Zone, 1997

Climate Zone (CZ) 5 OCZ 4 CZ 3 OCZ 2 CZ 1

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In 1978, heat pumps were relatively rare, used in only 1.2 million housing units. By 1997, the use of heat pumps increased eightfold to 9.7 million. Between 1978 and 1997 the number of warm-air furnaces in use increased by 47 percent, from 38.4 million housing units to 56.6 million housing units. Over the same period, the number of housing units using a steam/hot-water system was unchanged. However, compared to the 15.9 million steam/hot water systems in use in 1987, the 13.4 million in use in 1997 represents a 16 percent decrease.

Percent of Housing Units

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Sources Energy Information Administration; 1997 Residential Energy Consumption Survey

These changes reflect both changes in construction of housing units, with duct work replacing pipes and radiators, and the new heating equipment and technology.

Out Go the Steam/Hot Water Systems

In 1978, when the first RECS was conducted, 18 percent of housing units used a steam/hot water system as their main space-heating equipment. In the 1997 RECS, the comparable percentage was 13 percent of housing units.

The modal age (the age category that included more systems than any other age category) of the steam/hot water equipment in place in 1997 was 19 or more years (Figure 3.10). Regardless of the age, a majority of the systems was found in housing units built before 1950. Most new systems were installed in older housing units. Of the 3.0 million housing units with a system less than 10 years old, 88 percent were in housing units built before 1980. Of the 614,600 systems that were less than 2 years old, only 7 percent were installed in housing units built in the 1990-97 period.

The combined distribution of steam/hot water systems by year of construction and climate zone (CZ) reveals that most steam/hot water systems were in older housing units located in colder climates (Figure 3.9).

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Sources: Energy Information Administration; 1997 Residential Energy Consumption Survey

When considering the replacement of space-heating equipment, the first factor is the heat distribution system. A housing unit that uses steam/hot water as its main spaceheating system is not a candidate for any type of warm-air system because the pre-existing pipes and radiators are an incompatible distribution system. Without changing the distribution system, the choice of a replacement heating system is limited to one using the same distribution system. Otherwise, the alternative is the installation of ducts that would support a central warm-air system or the use of space heaters in individual rooms. For new construction, the installation of duct work and vents for a warm-air system is less expensive that the installation of the piping and radiators required for a steam/hot water system, thus accounting for the installation of so few systems of this latter type in the 1990s. In addition, the increased population of central airconditioning in new construction requires the installation of duct systems.

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Percent of Housing Units

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In 1978, when the first RECS was conducted, 2 percent of housing units used heat pumps as their main space-heating equipment. In the 1997, the comparable percentage was 10 percent of housing units.

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Sources: Energy Information Administration; 1997 Residential Energy Consumption Survey.

The combined distribution of heat pumps by year of construction and climate zone reveals that most were in newer housing units located in warmer climates (Figure 3.11).

Only 18 percent of the heat pumps were located in housing units built before 1970, and only 10 percent were located in the two most northern climate zones (CZ 1 and CZ 2). This

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Two sets of detailed data tables are presented in this report. The first set describes Housing Characteristics of 1997 U.S. housing units and the second set describes the Energy Consumption and Expenditures of those housing units. Reference Guides for each set of tables are provided.

Due to space limitations in this volume, not all of the large number of detailed data tables that have been prepared are presented in this report. For both sets of tables, only those tables not shaded in the Reference Guides are included. Also, only the Housing Characteristics tables that present data in terms of counts of millions of U.S. households (the tables with an “a” suffix) are included. The complete set of tables are available on the “Households" Web site at http://www.eia.doe.gov/emeu/consumption.

Organization and Categories of Data in the Tables

Topical Groups

The Housing Characteristics tables are organized into seven topical groups:

1. Housing Unit Characteristics—Location, type, ownership, age, size, and year of construction of U.S. Housing Units.

2. Household Characteristics—Household demographic and income characteristics.

3. Space Heating—Types of heating fuel and equipment used for main and secondary space heating purposes.

4. Air-Conditioning—Selected household characteristics, including location, number of rooms cooled, and air-conditioning usage.

5. Appliances—Frequency and characteristics of energy-intensive appliances found in most households.

6. Usage Indicators—The usage of heating and cooling equipment, including thermostat settings at various times of the day, equipment using hot water, and other appliances.

7. Home Office Equipment-Presence of office equipment in households.

The Consumption and Expenditures tables are organized into five topical groups:

1. Total Energy—Total and per-household consumption of major fuels, by Btu and physical units, and end use. Expenditures data include total and per-household expenditures for each major fuel, the cost of each of the major fuels per million Btu and per physical unit, and the total and per-household expenditures by end-use.

2. Space Heating—Total and per-household consumption of major fuels for space heating by Btu and physical units. Expenditures data include total and per-household expenditures for each major fuel used for space heating. Also presented are heating degree days and heated square footage data, both determinants of space-heating fuel consumption and expenditures.

3. Electric Air-Conditioning—Total and per-household electric air-conditioning consumption by kWh and Btu. Expenditures data include total and per-household expenditures. Cooling degree-days and cooled square footage data, both determinants of space-heating fuel consumption and expenditures, are included.

4. Water Heating—Total and per-household consumption of major fuels for water heating by Btu and physical units. Expenditures data include total and per-household expenditures for each major fuel used for water heating.

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5. Appliances—Total and per-household consumption of electricity for refrigerators and lighting, and major fuels for all other appliances by Btu and physical units. Expenditures data include total and per-household expenditures.

Table Headings

The data for each topical group for both the Housing Characteristics tables and the Consumption and Expenditures tables are presented by:

1. Climate Zone-Each of the five main U.S. Climate Zones, which are climatically distinct areas determined according to the 30-year average of the annual heating and cooling degree-days (available only on our Web site).

2. Year of Construction—Units constructed before 1939, each decade through 1989, and 1990-1997.

3. Household Income-Four income brackets and low income households.

4. Type of Housing Unit—Four main types of housing units: single-family homes, two to four unit multifamily units, five or more unit multifamily units, and mobile homes.

5. Type of Housing Unit Owner-Occupied (Housing Characteristics only)— Type of housing units for owneroccupied units (available only on our web site).

6. Type of Housing Unit Renter (Housing Characteristics only)Type of housing units for rented units (available only on our Web site).

5. Household Demographics (Consumption and Expenditures only)—Total and per-household consumption and expenditures by household size, household income, and demographic characteristics of the householder.

6. Usage Indicators (Consumption and Expenditures Only)—Total and per-household consumption and expenditures by indicators that affect energy consumption and expenditures, including size of the housing unit, occupancy during the day, activities in the housing unit, thermostat settings, and use of air-conditioning and appliances.

7. Four Most Populated States—Four most populated States: New York, Florida, Texas, and California (available only on our Web site).

8. Urban/Rural Location-Housing units in cities, towns, suburbs, and rural locations as characterized by the respondent in the household interview (available only on our Web site).

9. U.S. Census Regions and Divisions-Northeast—The Northeast Census Region and the two Census Divisions within that Region (available only on our Web site).

10. U.S. Census Regions and Divisions-Midwest—The Midwest Census Region and the two Census Divisions within that Region (available only on our Web site).

11. U.S. Census Regions and Divisions-South—The South Census Region and the three Census Divisions within that Region (available only on our Web site).

12. U.S. Census Regions and Divisions-West—The West Census Region and the two Census Divisions within that Region (available only on our Web site).

13. U.S. Census Regions—The four U.S. Census Regions.

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