ETDF (Energy to Demand Factor) is defined below: The ratio of the average demand between 2 PM and 6 PM on summer weekdays to the total annual energy usage is taken from an electric water heater metering study performed by BG&E (pg 95 of Source 2). The parameters in the above equation are listed in Table 249. Table : Solar Water Heater Calculation Assumptions Component Unit Values Source EFbase , Energy Factor of baseline electric Fraction See Table 250 3 water heater Default= 0.904 3 (50 gallon) EFee , Year-round average Energy Factor of Fraction EDC Data Gathering EDC proposed solar water heater Data Gathering Default=1.84 1 HW , Hot water used per day in gallons 50 4 Thot , Temperature of hot water 123 5 Tcold , Temperature of cold water supply 55 6 Default Baseline Energy Usage for an electric Calculated 3,338 water heater without a solar water heater (kWh) ETDF , Energy to Demand Factor (defined 0.00008047 2 above) Federal standards for Energy Factors (EF) are equal to 0.97 (.00132 x Rated Storage in – Gallons). The following table shows the baseline Energy Factors for various tank sizes: Table : Minimum Baseline Energy Factors Based on Tank Size Tank Size (gallons) Minimum Energy Factors 40 0.9172 50 0.9040 65 0.8842 80 0.8644 120 0.8116
ETDF (Energy to Demand Factor) is defined below: The ratio of the average demand between 2 PM and 6 PM on summer weekdays to the total annual energy usage is taken from an electric water heater metering study performed by BG&E (pg 95 of Source 2). The parameters in the above equation are listed in Table 249. Table : Solar Water Heater Calculation Assumptions Component Unit Values Source EFbase , Energy Factor of baseline electric water heater Fraction See Table 250 3 Default= 0.904 (50 gallon) 3 EFee , Year-round average Energy Factor of proposed solar water heater Fraction EDC Data Gathering EDC Data Gathering Default=1.84 1 HW , Hot water used per day in gallons 50 4 Thot , Temperature of hot water 123 5 Tcold , Temperature of cold water supply 55 6 Default Baseline Energy Usage for an electric water heater without a solar water heater (kWh) Calculated 3,338 ETDF , Energy to Demand Factor (defined above) 0.00008047 2 Federal standards for Energy Factors (EF) are equal to 0.97 – (.00132 x Rated Storage in Gallons). The following table shows the baseline Energy Factors for various tank sizes: Table : Minimum Baseline Energy Factors Based on Tank Size Tank Size (gallons) Minimum Energy Factors 40 0.9172 50 0.9040 65 0.8842 80 0.8644 120 0.8116
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