Many people in the U.S. can produce more than half their domestic hot water needs with a solar hot water system. In
Arizona and other southern regions of the US this can be more than 80% savings. A solar hot water system costs more than a conventional water heater, typically between $7,000 and $8,000. However, after rebates and tax incentives the cost to the client for a new solar hot water heater including a new tank is $2 – 3,000. Homeowners may want to budget for routine maintenance on some units to include periodic checks on the pH of the system’s with glycol solution.
A gas water heater should never be used as the only tank in a solar hot water system. In a solar storage tank, water stratifies by temperature; cool water from the bottom of the tank is pulled up to the collectors on the roof to be heated then returned to the top of the tank. The colder the incoming water, the higher the solar collector’s efficiency. In a single tank system, the electric element or gas flame keeps the stored water hot, leaving no cold water available to send to the solar collectors. Solar hot water systems can be either active or passive. Most solar hot water systems use a pump to move fluid through one or two collectors. Thermosiphon systems, suitable for simple domestic hot water systems in frost-free climates, rely on natural convection to move water.
As mentioned above, in most cases, credits or rebates can defray some of the cost of installing a solar water heater and are available from local utilities or state and federal governments. Solar
systems offer stability and predictability when it comes to energy costs and supply. That’s not something that any system running on fossil fuels can match.