1. 1 Revised Solar Water Heating Deemed Savings Estimates April 1, 2003

2. 2 Reason for Revisions Current “Deemed” Values based on system with 40 sq.ft. collector area Oregon Tax Credits and “Brightway” specifications cover three “generic” sizes –37.3 sq.ft. –60.0 sq.ft. –74.6 sq.ft.

3. 3 Analytical Approach Use Oregon Office of Energy “Savings” Estimates for Systems Approved for Tax Credit Estimate “Average” savings/sq.ft. collector area across all listed systems Use “curve fit” to establish savings for three system sizes

4. 4 Regression Fit for Solar DHW Systems with Tanks

5. 5 Regression Fit for Solar DHW Systems without Tanks

6. 6 Comparison of Regression Fit Results for 40 sq.ft. System Solar ZoneSavings for Systems w/Tank (kWh/yr) Savings for Systems w/o Tank (kWh/yr) Zone 1 1,818 1,930 Zone 2 2,161 2,324 Zone 3 2,272 2,391

7. 7 Comparison of Regression Fit Results for 80 sq.ft. System Solar ZoneSavings for Systems w/Tank (kWh/yr) Savings for Systems w/o Tank (kWh/yr) Zone 1 2,441 2,561 Zone 2 2,752 2,917 Zone 3 2,964 3,139

8. 8 Regression Fit Results for Deemed Solar DHW Systems Solar ZoneCollector Area = 37.3 sq. ft. (kWh/yr) Collector Area = 60.0 sq. ft. (kWh/yr) Collector Area = 74.6 sq. ft. (kWh/yr) Zone 1 1,800 2,200 2,400 Zone 2 1,900 2,300 2,500 Zone 3 2,100 2,600 2,700 Zone 4 2,400 3,000 3,200 Zone 5 2,500 3,200 3,400