Solar Water Heating System Calculator

Below is a calculator to help you determine the savings and payback period for a solar water heating system. The general guideline is that a single person consumes 20 gallons of hot water per day. So, for a family of 4 the total cosnumption would be 80 gallons per day. It is also recomended that capacity of the storage take be equal to the daily demand.

The payback period is influenced heavily by the incentives available. To learn what incentives are available in your area, refer to the DSIRE website.

Water Heater Characteristics
Physical		Thermal
Tank Diameter (feet)		Water Inlet Temperature (Degrees F)
Capacity (gallons)		Ambient Temperature (Degrees F)
Surface Area (calculated - sq ft)		Hot Water Temperature (Degrees F)
Effective R-value		Hot Water Usage (Gallons per Day)
Energy Use
		Heat Delivered in Hot Water (BTU/hr)
		Heat loss through insulation (BTU/hr)

Conventional Water Heating
	Gas	Propane	Oil	Electric
Overall Efficiency
Conversion Efficiency				0.98
Power Into Water Heater	BTU/hr	BTU/hr	BTU/hr	BTU/hr
Utility Costs
Utility Rates	$/Therm	$/Gal	$/Gal	$/kWh
Yearly Water Heating Cost	$	$	$	$
Solar Economics
Solar Water Heater Cost: $		Percentage Solar Capacity: %
Federal Incentive: %		Local Incentive: %
Local Incentive: $		Local Incentive: $/W
Payback Time for Solar System	years for gas	years for propane	years for oil	years for electric

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