Solar water heaters in Florida: are they worth it?

The Department of Energy says water heating bills should drop 50% to 80% on average with a solar water heater, though the systems cost more to buy and install than conventional water heaters. ENERGY STAR says a certified solar system can cut annual hot water costs in half and is designed to work with an electric or gas backup.

Water heating is a meaningful slice of the bill: UF/IFAS puts it at 13% to 17% of a home's energy use. See why your FPL bill is so high.

• Active systems pump water or a heat-transfer fluid through rooftop collectors. Indirect active systems, which circulate a non-freezing fluid, are popular where freezes happen, according to DOE.
• Passive systems move water without pumps. DOE says they're typically less expensive but usually less efficient.
• Batch (ICS) systems store water in the collector and work best where temperatures rarely fall below freezing, which suits South Florida better than the Panhandle.

Florida law (s. 377.705) requires solar systems sold in the state to meet Florida Solar Energy Center standards. FSEC no longer tests solar thermal equipment itself and accepts SRCC or IAPMO certifications, so ask for the system's certification.

Often, yes. DOE says heat pump water heaters are two to three times more efficient than conventional electric water heaters. In a Florida Solar Energy Center side-by-side test, the heat pump water heater used the least electricity, about 2.75 kWh a day, slightly less than a solar water heater with a PV-powered pump at about 3.03 kWh a day.

At about 1,004 kWh a year, that heat pump water heater would cost about $138 a year on FPL at our estimated rates, and about 2 panels on your roof would offset it. FSEC researchers projected in 2017 that a PV-powered heat pump water heater "likely costs half" what a solar thermal system does, with no freeze protection needed.

Panels also do more than heat water: under Florida's full-retail net metering, every kWh they make offsets any part of your bill. See how many solar panels you need.

Not federal ones anymore. The 30% federal credit (25D), which covered solar water heating, ended for systems installed after December 31, 2025, and the IRS says the energy efficient home improvement credit (25C), which covered heat pump water heaters, ended for property placed in service after 2025.

Florida's sales tax exemption still applies: it covers solar energy equipment used for water heating. Florida's solar rights law also protects solar collectors, so an HOA can't ban a solar water heater, though it can pick the roof spot. See Florida solar incentives and Florida HOA solar rules.

Yes. By 1941, a Florida company had installed more than 60,000 solar water heaters, and over half of Miami's population heated water with the sun, according to Invention & Technology. The industry faded after World War II as electric rates fell and electric water heaters were heavily promoted.

Interest returned in the 1970s: the Legislature created the Florida Solar Energy Center to research solar energy and test and certify solar systems, the role behind today's certification rule.

The Florida Solar Energy Center's long-standing rule of thumb is 10 square feet of collector and 20 gallons of storage per person, so a family of four typically needs about 40 square feet of collector and an 80-gallon tank. The U.S. Department of Energy says very sunny climates can use as much as 2 gallons of storage per square foot of collector, which matches that ratio.

Periodic checkups. The Department of Energy recommends having a solar heating professional inspect the system periodically, and says glycol-based systems stay freeze-protected only while the antifreeze concentration is right; the propylene glycol has to be replaced from time to time.

North of Central Florida, PNNL's Building America guide says passive collectors may need a freeze valve and better-insulated outdoor piping. Follow the maker's schedule for fluid and anode checks.

• A solar water heater makes sense if your current tank is failing, you use a lot of hot water, and you have roof space to spare after panels.
• A heat pump water heater plus panels usually saves more per dollar and covers the rest of your bill too. A heat pump unit needs space and air around it, so ask your installer about placement in a garage or utility room.
• Pool heating is a different product; see solar for pool homes.