Solar pool heaters
The only heating you can buy whose running cost is genuinely zero. Here is what that costs you in control.
Quick picks
One solar system, the cover that makes it worth having, and the fallback for anyone whose site or climate will not support panels.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | No photo The pick SmartPool SunHeater S601P Solar Heating System Panels that plumb into the return line. Zero fuel cost, and the manufacturer claim is a cumulative figure, not an afternoon. | Adding real heat with no running cost, on a sunny site | |
| 2 | No photo Buy this alongside it Sun2Solar 1200 Series Crystal Clear Solar Cover Solar panels put heat in during the day. A cover is what stops it leaving at night. | Most pools, most budgets — the default recommendation | |
| 3 | No photo If the sun will not do it Hayward HeatPro Pool Heat Pump The controllable alternative, at about $10.75 per million BTU delivered. | Lowest running cost per degree when you want real temperature control |
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
What solar pool heating actually is
A solar pool heater is not a photovoltaic panel and does not make electricity. It is a collector — a mat or panel of black tubing — that your existing pump pushes pool water through. The sun warms the water in the tubes, and the warmed water goes back into the pool.
That simplicity is the whole appeal. There is no combustion, no gas line, no additional electrical service, no compressor and no refrigerant. The circulation pump is already running for filtration, so there is no additional energy cost attributable to the heat at all. Running cost is genuinely $0.00 per million BTU, which nothing else on this site can say.
The honest trade
You get whatever the sun delivered that day. There is no thermostat in any meaningful sense, and the failure mode is specific and predictable: on a cool, cloudy stretch in the shoulder season — exactly when you most want heat — solar panels deliver very little.
That is not a defect, it is the mechanism. It means solar heating is excellent at extending a warm season at the margins and poor at rescuing a cold week. If your ambition is a few more usable weeks in June and September, this is the right technology. If it is a reliable 84 degrees in April, it is not.
What to expect, quantified
Bob Vila describes the SunHeater S601P as able to “boost pool water temperature by as much as 15 degrees Fahrenheit” with ample sunlight. Read the phrasing carefully: as much as, and with ample sunlight. That is a cumulative ceiling reached over days of good sun — not something you will watch happen in an afternoon.
| Clear midday sun on a 16 x 32 pool surface | about 105,987 BTU/hr |
| That alone gives | about 0.66°F per hour |
| Panels add collector area on top of the pool surface | |
| But the ceiling is still the sun's daily energy budget |
Derived from NASA’s published energy budget. Panels help because they add collecting area and absorb far more efficiently than open water — but no arrangement of them beats a whole day of sunshine into a whole day of sunshine. The full derivation.
What decides whether it works at your house
- Unshaded collector area. The rule of thumb in the trade is collector area roughly equal to 50-100% of the pool’s surface. That is a lot of roof, and it has to be unshaded during the middle of the day.
- Orientation. South-facing is best in the northern hemisphere. East or west works with more area.
- Plumbing. The panels go inline after the filter. This is real plumbing work if the panels are on a roof, and it is where the install cost lives.
- Freeze protection. Panels full of water in a hard freeze split. In a climate that freezes, they have to drain down for winter.
Pair it with a cover, always
Solar panels and a solar cover do different jobs and the combination is much stronger than either alone. The panels add heat during the day. The cover stops that heat leaving overnight — attacking the roughly 70% of loss DOE attributes to evaporation.
Buying panels without a cover means spending real money collecting heat and then letting most of it evaporate away by morning. If the budget only stretches to one of them this season, buy the cover.
DIY is a genuine option here
This is the one heating technology where a home-built version is not a fantasy: black poly tubing on a rack, plumbed into the return, is the same physics as a commercial panel at a fraction of the cost. We work through what is actually involved — including the parts of it that are more work than the internet suggests.
Every pick, in detail
What each one publishes, what is good and bad about it, and — the section this category usually omits — what we could not judge without owning one.
SmartPool SunHeater S601P Solar Heating System
Solar panels that plumb into the return line and heat the water with sunlight rather than fuel, which puts their running cost at zero — the only entry in the whole heating category where that is true. The trade is that you cannot dial in a temperature: the panels deliver what the sun gives them on the day, and on a cloudy week they deliver very little.
Best for Adding real heat with no running cost, on a sunny site
| Type | Roof or ground-mounted solar collector panels, plumbed inlineThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Running cost | $0 in fuelThe circulation pump is already running for filtration. There is no additional fuel or electricity cost attributable to the heat. | Our arithmetic |
As much as 15 degrees F
Claimed by Bob Vila, describing the S601P. Conditions: Stated as requiring ample sunlight; no time period given. Source
Note the phrasing: with ample sunlight it can boost temperature by as much as 15 degrees. That is a cumulative ceiling reached over days of good sun, not a figure you will see in an afternoon.
- Zero fuel cost, forever — nothing else in this category can say that
- No combustion, no gas line, no additional electrical service
- Panels can be added to as the budget allows
- You get the sun's schedule, not yours
- Needs real unshaded mounting area, and plumbing work to install
- Does nothing on a cold cloudy week, which is when you most want it
- Actual heat output at your latitude, roof pitch and shading
- How the panel material survives a decade of UV and freeze cycles
- Whether the included fittings suit your existing plumbing
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
Sun2Solar 1200 Series Crystal Clear Solar Cover
The value pick, and the one whose logic actually holds up. A clear cover transmits more sunlight into the body of the pool instead of absorbing it at the surface, and 12 mil is the point where lifespan stops being the limiting factor. Bob Vila measured this and the 16-mil blue at the same 4 to 5 degrees in an hour, so you are paying less for the same measured result and giving up some years of service life.
Best for Most pools, most budgets — the default recommendation
| Thickness | 12 milThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Color | Clear | Retail listing |
| Stated lifespan | 3 to 4 years for the 12-mil clear tierSwim University's published figure for 12-mil clear covers generally. | Retail listing |
| Bubble side | Bubbles face the water | Published standard |
4 to 5 degrees F in one hour
Claimed by Bob Vila, measured across all covers in their group. Conditions: One hour under 2pm sun on 89 to 92 degree F days. Source
- Clear transmits more light into the water instead of stopping it at the surface
- 12 mil is the sweet spot: real service life without 16-mil bulk
- Cheaper than the 16-mil tier with no measured heating penalty
- Shorter published lifespan tier than 16 mil
- A clear cover shows algae and debris more obviously, which some people dislike
- Whether clear genuinely outlasts or under-lasts blue in the same thickness
- Real-world tear resistance at a pool with rough edges
- How much the clear material clouds over a season of UV
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
Hayward HeatPro Pool Heat Pump
If you are heating a pool with electricity, this is the shape of machine to do it with. A heat pump moves heat instead of making it, and at the assumptions we publish it delivers a million BTU into the water for about a fifth of what an electric resistance heater costs to deliver the same. It is slower than gas and it fades as the air gets colder, which is exactly when you want it — that trade is the whole decision.
Best for Lowest running cost per degree when you want real temperature control
| Type | Air-source heat pumpThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Rating convention | Rated by BTU/hr OUTPUTThis is the trap in the category. Gas heaters are rated by fuel INPUT, heat pumps by heat OUTPUT. A 140,000 BTU heat pump and a 140,000 BTU gas heater do not deliver the same heat. | Published standard |
| Cost per million BTU delivered | About $10.75 at our published assumptionsUS average residential electricity at 18.34 cents/kWh (EIA, June 2026) and an assumed COP of 5.0. Both are substitutable on our running-cost calculator. | Our arithmetic |
- Cheapest running cost per delivered BTU of any controllable heater
- No gas line, no combustion, no flue
- Holds a set temperature rather than depending on the weather
- Slow — expect most of a day to move a full-size pool ten degrees
- Efficiency falls with air temperature, so it is weakest in the shoulder season
- High purchase price against a gas heater of comparable output
- The COP this specific unit achieves at your conditions
- Compressor and control-board longevity
- Noise at the distance your deck actually sits from it
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
Questions people actually ask
Do solar pool heaters actually work?
How much will a solar pool heater raise my temperature?
How many solar panels do I need for my pool?
Do solar pool heaters work at night?
- Pool heater roundup: the 8.33 BTU per gallon per °F figure, attributed on the page to Alicia Toedter of Leslie'sBob Vila · read 2026-09-02
- Earth's energy budget: 1,360 W/m² of solar energy at the top of the atmosphere, about 48% absorbed at the surfaceNASA Earth Observatory · read 2026-09-02
- U.S. Department of Energy pool-energy figures (evaporation share, BTU per pound evaporated, cover savings, recommended temperatures, wind effect)Recreonics, reproducing and attributing the U.S. Department of Energy · read 2026-09-02
- Average retail price of electricity to US residential customers: 18.34 cents/kWh, June 2026U.S. Energy Information Administration · read 2026-09-02
- Energy content conversion factors: 3,412 BTU per kWh, 1,036 BTU per cubic foot of natural gas, 91,452 BTU per gallon of propaneU.S. Energy Information Administration · read 2026-09-02
Every URL above was fetched and returned content on the date shown. Where a figure is ours rather than somebody else’s, the arithmetic is on the page and on the methodology page. If you find an error in it, we would genuinely like to know.
Read next
Building your own solar pool heater
The physics of a homemade solar collector, how much area you actually need, and an honest list of the parts that take longer than the videos suggest.
Solar panels vs a heat pump
Free-to-run solar collectors against a controllable heat pump. What each one is genuinely good at, and the case for running both.
How to heat a pool
The complete walkthrough: what your pool actually needs in BTU, every heating option priced per delivered million BTU, and the order to try them in.
Solar pool covers worth buying
Ranked on the specifications that actually differ between covers — thickness tier and published lifespan — because the only hands-on test in this category found no heating difference at all.
The cheapest way to heat a pool
Cheapest to buy is a cover. Cheapest to run is solar, then a heat pump. The arithmetic for both, and a spending order that works at any budget.