Solar water heating in Florida: thermal vs panels + heat pump

A solar water heater (solar thermal) uses roof collectors to heat water directly, and per the DOE it can reduce the hot water bill by 50% to 80%. In Florida it works very well. The question in 2026 is no longer whether it works, but whether it beats the alternative: photovoltaic panels that produce electricity and a heat pump water heater that uses it 2-3 times more efficiently than a standard heater. For most homes that plan to install panels, the second option wins; thermal has its place when panels are not in the plan.

How does solar thermal work?

The DOE describes two families:

• Active systems. Pumps and controls move water (or an antifreeze fluid, rarely needed in Florida) through the collectors and into the tank.
• Passive systems. No pumps: water rises by convection from the collector to the tank, which usually sits above it. Simpler and cheaper, less efficient.

The most common residential collectors are flat plates (a glazed box with tubes inside) and, less so in Florida, evacuated tubes. Every system includes a tank with electric or gas backup for nights and cloudy days. Water heating is about 18% of home energy use (DOE), so cutting half or more of that is real savings.

Thermal vs photovoltaic + heat pump: the honest comparison

When you are already putting up panels, dedicating roof to thermal collectors is usually the worse deal: every square foot of collector is a square foot less of panel that could produce kWh for everything, with surplus credited. A heat pump water heater fed by those panels does the same job with less roof and fewer parts.

Heads up: for years solar thermal was sold in Florida with the 30% federal credit as the central argument. Per the IRS FAQs following the OBBB law, the 25D credit does not apply to expenditures after December 31, 2025. If in 2026 it is offered “with the 30%,” the argument has expired. Confirm with your tax preparer and ask for the numbers without the credit.

When does solar thermal make sense?

• You are not installing photovoltaic panels (partially shaded roof, municipal utility without net metering, a subscription contract that does not apply, or you simply do not want them). Then thermal attacks the 18% of consumption on its own.
• Lots of hot water and little roof. Heated pool, large family, hot tub: thermal delivers heat more efficiently per square foot than converting sun to electricity and then to heat.
• You already have the system installed and working: maintaining it is almost always worth more than replacing it.
• Pool heating. This is the use where solar thermal wins almost always in Florida: large volume, low temperature, no backup needed.

When it does NOT make sense

• You are installing photovoltaic panels: use that roof for panels and add a heat pump water heater.
• The roof has under 5-10 years of life: collectors are heavy and bolted; read roof before solar.
• You have untreated hard well water: collectors scale up; check Florida water first.
• You use little hot water: absolute savings are small and payback is slow.
• It is sold to you with a federal credit in 2026: ask for the numbers without it.

What to check before you decide

• Will you install photovoltaic panels in the next few years? If so, the decision is usually heat pump, not thermal.
• Usable south-facing roof space, shade and roof condition.
• Your hot water use: people, showers, pool or hot tub.
• Quote with and without backup, with system type (active/passive) and a Florida maintenance plan.
• If pool heating interests you, get a separate quote: thermal usually pays there. And to size the whole roof, start with how many panels I need.