An Economic Analysis of Solar Water & Space Heating.

Solar system designs for 13 cities were optimized so as to minimize the life cycle cost over the assumed 20-year lifetime of the solar energy systems. A number of major assumptions were made regarding the solar system, type and use of building, financial considerations, and economic environment used in the design optimization. Seven optimum designs were developed for each city. In each case, comparisons were made with electric, oil, and natural gas water heating; and with electric resistive, electric heat pump, oil, and natural gas space heating. In each case, the backup conventional system used in the analysis was assumed to be the same as the competitive conventional system used in the analysis. To incorporate geographic variation, the study incorporated different climatic data, current 1976 incremental conventional fuel costs, building energy loads, and collector elevation angles for each city. Based on comparison with conventional energy costs, solar water heating and solar space heating installed at an equivalent system cost of $20 per square foot of collector are competitive today against electric resistance systems throughout most of the U.S. If the cost should be reduced to $10 per square foot by 1980 through a combination of technical innovations and incentives, solar hot water and heat would be economically competitive against all residential fuel types. (Author/MLF)