What is the difference between solar thermal and photovoltaic?
Solar thermal captures the sun's energy as heat, while photovoltaic captures it as electricity. A solar thermal collector is a dark panel or a rack of glass tubes on the roof with fluid running through it. Sunlight heats that fluid, a pump moves it to a tank, and it warms your water, your pool, or a heating loop. A photovoltaic panel is a grid of silicon cells that produce a DC electric current the moment light hits them; an inverter turns that into the AC power your house uses. See how do solar panels work for the PV side and solar water heaters for the thermal side.
That difference in output is the whole decision. Heat from a solar thermal system can only do heating jobs, so it offsets one slice of your energy bill. Electricity from PV can run lights, the fridge, the AC, an EV charger, and an electric or heat-pump water heater, so it can offset your entire bill and then some. A solar thermal collector and a PV panel are not interchangeable; one heats a fluid, the other powers your home. That is why almost all new residential solar in the US is PV, not thermal.
Is solar thermal more efficient than photovoltaic?
Yes, on paper: a solar thermal collector turns about 60 to 70 percent of the sunlight hitting it into usable heat, while a PV panel converts only about 15 to 22 percent of it into electricity. Per square foot, solar thermal captures far more raw energy, which is why it needs so much less roof area to cover a family's hot water. If your only goal is hot water and you judge by efficiency alone, thermal looks like the clear winner.
The catch is that efficiency is not the same as value. Solar thermal's high number only counts if you can actually use all that heat, and a home's hot-water demand is small and easy to overshoot in summer. PV's lower efficiency is spread across a much larger, more useful output: electricity you can send to any appliance, store in a battery, or push back to the grid for credit through net metering. Measured by useful output per dollar, not raw capture, PV is the more productive system for most homes. Compare monocrystalline vs polycrystalline if you want to push PV efficiency higher.
Which is cheaper, solar thermal or photovoltaic?
For a hot-water-only goal, solar thermal costs less upfront, roughly $3,000 to $9,000 installed versus $18,000 to $30,000 for a whole-home PV array. But that is not a fair fight, because the PV array is doing far more work. The honest way to compare is by the same job: cover your hot water. A dedicated solar thermal system does it with two collectors and a tank, while PV does it by running a heat-pump water heater on some of the panels you were installing anyway. See how much does solar cost for the PV side of the math.
This is why PV has taken over. Panel prices have dropped by roughly 90 percent over the last decade, so a few extra PV panels plus an efficient electric water heater now often beats a standalone solar thermal setup, and you avoid the pump, controller, and antifreeze loop that thermal systems need to maintain. Solar thermal still makes sense when the heat load is huge and constant, which is exactly why it dominates one market: pools. Read solar pool heater cost for that case. Every figure here is an estimate that moves with your rates, sun, and installer, so get local quotes and see our disclaimer.
When is solar thermal worth it over photovoltaic?
Solar thermal is worth it in two situations: heating a pool, and cutting a high hot-water bill in a sunny climate. A solar pool heater has almost no competition; it moves a large, steady heat load cheaply and pays back fast, which is why it is the most common solar thermal product sold. For domestic hot water, thermal can pay off if you use a lot of it and currently heat with expensive electricity or propane, and you live somewhere with strong year-round sun. Outside those cases, the small hot-water load and the extra maintenance make it a hard sell against PV.
For nearly everything else, choose PV. It offsets your whole bill, has no moving parts, expands easily, and can cover hot water through a heat-pump water heater on the side. One thing that changed the math for both: the 30 percent federal residential solar tax credit under Section 25D expired for systems placed in service after December 31, 2025, and that credit covered solar water heating as well as PV. So a homeowner buying either system now gets no federal residential credit; plan without it. Weigh the full picture in pros and cons of solar panels, and size the PV side with the solar panel calculator.
Solar thermal wins on
- +Captures about 60 to 70 percent of sunlight as heat, far more per square foot
- +Needs only a collector or two for a family's hot water, so it uses little roof area
- +Cheaper upfront if your only goal is hot water or a warm pool
- +The clear winner for pool heating, a large and steady heat load
Photovoltaic (PV) wins on
- +Makes electricity that runs anything, so it offsets your whole bill, not one load
- +Prices have fallen roughly 90 percent in a decade, undercutting dedicated thermal
- +No moving parts; minimal upkeep beyond a rinse and one inverter swap
- +Works with net metering and batteries, and can heat water via a heat-pump tank
The verdict
Buy photovoltaic for the house, and use solar thermal only as a targeted add-on. For almost every homeowner, PV is the better choice: it offsets your entire electricity bill, needs little maintenance, works with net metering and batteries, and has gotten so cheap that a few extra panels running a heat-pump water heater usually beat a standalone solar thermal system. Reserve solar thermal for the two jobs it still owns, heating a pool and cutting a high hot-water bill in a sunny climate. Note that the 30 percent federal residential credit expired for systems placed in service after December 31, 2025, and it covered both technologies, so plan without it. Size the electricity side with the solar panel calculator. This is general information, not financial or professional advice; see our disclaimer.
Related: Solar panel calculator: size your system, Solar water heaters: how they work and cost, Solar pool heaters: how they work and cost.
Frequently asked questions
Is solar thermal better than PV?
For most homes, no. Solar thermal is more efficient at capturing sunlight as heat, about 60 to 70 percent versus 15 to 22 percent for PV, but it only produces heat, so it offsets a single load. PV produces electricity that runs your whole house, works with net metering and batteries, and has gotten so cheap that a slightly larger PV array plus an efficient water heater usually beats a dedicated thermal system. Solar thermal is better only for pool heating or a high hot-water bill in a sunny climate.
What are the disadvantages of solar thermal?
Solar thermal only makes heat, so it offsets water, pool, or space heating and nothing else, which is a small slice of most bills. It has more to maintain than PV: a pump, a controller, and an antifreeze loop that needs periodic service. It can overproduce heat in summer with nowhere to send it, it does not work with net metering or batteries, and the federal residential tax credit that once helped pay for it expired for systems placed in service after December 31, 2025.
Is solar thermal worth it?
It is worth it for two jobs. Heating a pool is the strongest case; a solar pool heater moves a large, steady heat load cheaply and pays back fast. Cutting a high domestic hot-water bill can pay off if you use a lot of hot water, currently heat it with expensive electricity or propane, and live somewhere sunny year-round. For general home energy, PV is the better value because it offsets everything, not just heat.
How long does solar thermal last?
A solar thermal system lasts about 20 to 25 years, a bit less than PV's 25 to 30 years. The collectors themselves are durable, but the pump, controller, and heat-transfer fluid are wear items you should expect to service or replace over that span. PV, by contrast, has no moving parts, so beyond one inverter swap it needs very little.
What is solar PV and solar thermal combined?
That is a hybrid panel called PVT, or photovoltaic-thermal. A single panel generates electricity from PV cells on the front while a fluid loop behind it captures the waste heat, giving you both power and hot water from the same roof area. PVT is clever and space-efficient but niche and pricier, with far fewer installers. For most homes, separate PV panels plus a heat-pump water heater is simpler and cheaper than a PVT array.