A well-maintained, high-quality solar water heating system typically last for 20 years. Some systems can last even longer: some systems installed in the 1970s are still going strong. By comparison, conventional storage water heaters will last around 10-15 years. Regular maintenance from experienced contractors is key to maintaining the longevity of the system, as well as keeping its performance up and maintenance costs down in the long run.
Researchers at the Florida Solar Energy Center have suggested that approximately 2% of the cost of your system should be budgeted for maintenance every year. Most manufacturers and installers suggest having a site inspection by a contractor every two to three years, which can range in price, but overall is a very low out-of-pocket cost. If you use a system that circulates an antifreeze (glycol) fluid, the fluid should be changed out at least once every 5 years. Waiting until your system is damaged will likely cost much more than what regular maintenance would have cost over that time period. Some installers will provide maintenance service contracts that include regular inspections and servicing, but you may find a better quote from a different contractor.