Solar Hot Water Heating

What is the "payback" on a solar hot water system?

Hot water is typically 25%-30% of the annual utility bill. Hot water for showers, dishwashing, and laundry costs about $110 a year per person (when LP gas costs $1.15/gallon or electricity costs 7 cents/Kwh). When electricity is 10 cents/kwh or LP gas is $1.60/gallon, it will cost about $646 per year to heat water for a four person household. A properly sized solar water heating system can be expected to save this household $480 to $600.