Cost to Install a Flat Plate water heating system

According to the Federal Energy Management Program Solar Water Heating Technology Alert, flat plate water heating systems range in price from about $2,000 to $4,000 installed for residential systems (for 40 to 80 gallons per day usage), and $2,000 to $50,000 for commercial systems (for 40 to 1700 gallons per day usage). Their chart below compares the percentage of water heating energy that solar can provide in various cities for a 48 square-foot flat plate solar hot water system based on average water usage for four persons.

Source: http://www.pnl.gov/techguide/16.htm