Energy Costs The amount that households spend for energy varies from household to household, even for households with similar characteristics. Percentiles can be used to show where in the entire range a particular household falls. A percentile can be defined as follows: given a set of numbers, a p-th percentile is a value where p percent of the number in the set are smaller than or equal to the value and (100-p) percent of the number in the set are larger than or equal to the value. In 1997, for example, 50 percent of the households in the country spent $1,247 or less for energy used in the home and 50 percent spent $1,247 or more (See Table 3.3). Hence, $1,247 was the 50th percentile (or median). Similarly, the 25th percentile was $885 and the 75th percentile was $1,676. The spread between the 25th and 75th percentiles is one measure of the variability of energy expenditures. Total expenditures include the expenditures for electricity, natural gas, LPG, fuel oil, and kerosene used in the home. They exclude the cost of any wood or coal that was burned in the home, as well as the cost of motor gasoline used in automobiles or in other pieces of machinery that run on gasoline. This section gives percentiles for total energy expenditures. For households that do not pay for their energy directly (for example, when the rent includes the cost of electricity or other fuels), the cost of those fuels is estimated. Households where the expenditures were estimates are included in the process of estimating the percentiles. The procedure used to estimate the sampling error for the 1997 Residential Energy Consumption Survey was balanced half-sample replication. Although the procedure has some theoretical limitations when used to estimate the sampling error for percentiles, the complexity of the sample design prevented the use of a procedure that did not have these limitations. The resulting estimate of standard errors for the national median is $16 (Table 3.2). Hence, the 95 percent confidence interval for the median is $1,215 to $1,279. A review of the percentiles for each of the Census divisions shows that there are substantial differences among the divisions in their median expenditures (Figure 3.2 and Table 3.3). At the high end, the median for the New England Census Division is $1,569, and at the low end, the median for the Pacific Census Division is $892. The amount of variation in expenditures within Census divisions is even larger. In other words, the difference between the 10th and 90th percentiles within each division exceeds the difference between the median for the New England Census Division and the median for the Pacific Census Division. The "within" division differences can be partially explained by characteristics of the housing unit and households. Two of these are the size of the housing unit and the income of the household. Energy Information Administration Table 3.4. Annual Energy Expenditures Percentiles by Table 3.5. Annual Energy Expenditures Percentiles by Number of Rooms, 1997 Household Income, 1997 Figure 3.3. Annual Energy Expenditures Percentiles by Number of Rooms, Source: Energy Information Administration; 1997 Residential Energy Consumption Energy Information Administration Residential transportation represents almost one-half of total transportation energy. The 102 million U.S. households and 169 million regular drivers own or had regular use of 168 million vehicles, an average of 1.7 vehicles per household. That average was up slightly from an average of 1.6 vehicles per household in 1993. |