Solar panels vs a heat pump
Zero running cost against a thermostat. The right answer depends on whether your problem is the season or the week.
Quick picks
Both heating options and the cover that decides how much either of them achieves.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | No photo Free forever SmartPool SunHeater S601P Solar Heating System $0.00 per million BTU. No thermostat, no guarantees on a cloudy week. | Adding real heat with no running cost, on a sunny site | |
| 2 | No photo Controllable and still cheap Hayward HeatPro Pool Heat Pump $10.75 per million BTU delivered, on demand, whatever the weather. | Lowest running cost per degree when you want real temperature control | |
| 3 | No photo Multiplies either one Sun2Solar 1200 Series Crystal Clear Solar Cover Neither is worth much if the heat leaves overnight. | Most pools, most budgets — the default recommendation |
#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.
The trade in one line
Solar gives you free heat on the sun’s schedule. A heat pump gives you cheap heat on yours.
| Solar panels | Heat pump | |
|---|---|---|
| Running cost per million BTU | $0.00 | $10.75 |
| Control | None — you get what the sun gives | Thermostat |
| Works on a cloudy week | Barely | Yes |
| Works at night | No | Yes |
| Works in cold air | Poorly | Less well, but yes |
| Moving parts | None beyond your existing pump | Compressor and fan |
| Install | Plumbing plus mounting area | Electrical circuit plus a pad |
| Ongoing cost | Nothing | Your electricity bill |
Where solar wins outright
When the sun is already nearly enough. This is the honest sweet spot. If your pool is comfortable in July and marginal in June and September, solar panels are close to the perfect fix: they add heat exactly when there is sun to collect, which correlates well with the days you would otherwise be a couple of degrees short.
When running cost dominates your thinking. Zero is a number nothing else can match. Over ten seasons the difference against even a cheap-to-run heat pump is real money.
When you do not want another machine. No compressor, no refrigerant, no control board, nothing to service.
Where the heat pump wins outright
When you need the pool warm on a specific day. Solar cannot promise you Saturday. A heat pump can.
When your problem is the shoulder season. This is the one that surprises people. April and October are exactly when solar collectors have the least to work with — short days, low sun angle, frequent cloud. A heat pump is also weaker in cold air, but it still works. If your ambition is stretching the season at both ends rather than improving midsummer, the heat pump does more of it.
When you do not have unshaded area. Collector sizing guidance runs at 50 to 100% of pool surface area, unshaded, oriented toward the midday sun. A lot of houses simply do not have it.
Running both is the strongest option
They are complementary rather than competing, and the combination is genuinely better than either:
- Solar carries the sunny days for nothing, so the heat pump barely runs through the middle of the season.
- The heat pump covers the cloudy stretch and the specific Saturday.
- Your average cost per delivered BTU falls well below the heat pump’s number, because a large fraction of the season’s heat came free.
The reason people rarely do this is purchase cost, and it is a fair objection. If the budget only stretches to one, pick on the question in the next section.
The question that decides it
Is your problem the season, or is it this week?
If the answer is “the pool is basically fine but I want more of it” — solar. If it is “I want the pool warm when I decide to swim” — heat pump.
For the third option in this comparison, gas against a heat pump covers the speed argument in full.
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.
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.
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.
Questions people actually ask
Is a solar pool heater better than a heat pump?
Can I use solar panels and a heat pump together?
Which is better for extending the swim season?
- Average retail price of electricity to US residential customers: 18.34 cents/kWh, June 2026U.S. Energy Information Administration · read 2026-09-02
- US residential natural gas price: $24.09 per thousand cubic feet, June 2026U.S. Energy Information Administration · read 2026-09-02
- US residential propane price: $2.674 per gallon, week ending 30 March 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
- 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
- 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
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
Heat pump vs gas pool heater
The two options priced per delivered BTU and timed on the same pool, with the one question that decides which trade suits you.
Solar pool heaters
Solar collector panels: zero fuel cost forever, at the price of getting the sun's schedule instead of your own. Ranked, with the trade stated plainly.
What a pool heat pump costs to run
The heat pump running-cost derivation, what happens to it in cold air, and the two inputs that change the answer more than anything else.
Stretching the swim season
What actually adds weeks at each end of the season, why the shoulder season is a different problem from midsummer, and the order to spend in.
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.