Solar heaters for above-ground pools

How we judged these

Five criteria, stated before the ranking so you can see where every pick came from. The first one decides most of it.

• Collector area against your pool’s surface. A solar heater cannot deliver more heat than the sunlight landing on it, so the size of the thing catching sunlight is the specification that matters most — and the one listings most often leave you to work out yourself. The trade rule of thumb is collector area equal to 50 to 100% of the pool’s surface area.
• Plumbed collector or surface float. Two different mechanisms are sold under the same search term, and they are judged differently. We explain both below.
• What your filter pump can push. Above-ground pools run small pumps. A heater that wants more flow than yours makes is a heater that does not work at your house.
• Whether it will get used. A float that has to come out every time someone swims is worth less than its area suggests.
• What the maker publishes. A sizing rule you can use is worth more than a degrees claim you cannot check. We say which each product gives you.

The number that decides it: collector area

Start from your pool, not the product. An above-ground pool’s surface area is what the sun has to work against, and it is easy to work out for a round pool: pi times the radius squared.

Now put each product’s own published dimensions against the 18 ft round pool in the middle row, which is the most common above-ground size in this category:

That single calculation reorders the whole category. The dome heaters that dominate search results for this query are, by their own listed dimensions, the least capable product type you can buy for the job. A panel system is the only thing here that gets near the range, and even it wants company on a typical pool.

Two mechanisms, sold under one search term

Plumbed collectors — panels, mats and domes — sit beside or near the pool. Your filter pump pushes water through tubing inside them, the sun warms it, and it returns to the pool. They add heat and nothing else. They do nothing at night.

Surface floats — inflatable heaters and solar rings — sit on the water. They absorb some sunlight into the top of the pool by day, and more importantly they cover part of the surface, so they slow evaporation, which the Department of Energy puts at about 70% of a pool’s heat loss. That makes a float closer to a segmented cover than to a heater, and it is sized by how much of the surface it covers rather than by collector area.

Neither is better in the abstract. A plumbed collector adds heat you cannot otherwise get; a float keeps heat you would otherwise lose. On most above-ground pools the second problem is the bigger one, which is why a cover sits in the picks above. The cover-against-heater argument in full.

The panel system: SunHeater S421P

Two 2 by 20 ft tube-on-web polypropylene panels, 80 sq ft together, plumbed through the filter you already run, with flex-hose fittings in the box for a rigid-wall above-ground pool. It is the above-ground sibling of the inground S601P that our solar heater roundup discusses, with the same panels and a different connection kit.

Read its pool rating carefully. The listing calls one system perfect for above-ground pools up to 31 ft round. A 31 ft round pool has about 755 sq ft of surface, and by the collector rule it wants roughly 380 to 755 sq ft of panel — five to nine of these systems. The rating tells you where the fittings will reach, not how much the panels will heat. The same listing claims up to 15°F; SunHeater’s own page for the inground version, with identical panels, says up to 6 to 10°F under favorable conditions.

None of that makes it a bad product. It makes it the only product on this page that is honestly in the right size class, provided you buy enough of it and have the space — 4 by 20 ft of unshaded ground, rack or roof per system. The install guide covers mounting, plumbing and the pump.

The mat: Intex 28685E

The cheapest genuine plumbed collector sold for above-ground pools, and one of the few products in the category whose maker publishes real numbers: 47.25 by 47.25 in, rated for pools up to 8,000 gallons, and for filter pumps up to 1/3 HP or under 2,000 gallons an hour. That pump limit is the specification to check first, because a larger pump puts you outside Intex’s own rating.

At about 15.5 sq ft it is a small collector, and the 8,000-gallon rating is generous by the collector rule, which would put an 18 ft round pool at 8 to 16 mats. What makes it a sensible pick anyway is price and scale: on the smallest pools, and as a first step you can add to, it is the least expensive way to put real solar heat into the water. Our full Intex mat review.

The floats: GoFloats V2 and Solar Sun Rings

GoFloats deserves credit for doing what almost nobody in this category does: it publishes a sizing rule instead of a temperature. Each V2 heater is 5 by 5 ft and covers 25 sq ft; the listing says to cover at least 80% of the surface and to divide your pool’s area by 30 to get the count. For an 18 ft round pool that is about nine — three of the three-packs. It makes no degrees claim at all.

Solar Sun Rings are the round version of the same idea, at 60 inches across — about 19.6 sq ft each. Circles cannot tile a surface, so a pool full of rings always leaves more gap than a pool full of squares, and evaporation carries on through every gap in proportion. Our rings page works through what partial coverage does to the published cover savings.

The shared weakness of both is behavioral: they come out when people swim, and wind stacks them at one end. Their shared strength is the same: no plumbing, no pump question, and they go on a pool a blanket never would.

Why we would skip the dome

One disambiguation before you search. A solar dome heater is the small plumbed collector discussed above. A pool dome is an entirely different product — a transparent structure over the whole pool — and it is sold under a confusingly similar search term. That one is covered in pool domes and enclosures, and unlike the dome heater we do not tell you to skip it.

What your filter pump has to be able to do

Every plumbed collector here runs off your existing filter pump, which is why their running cost is zero — and why pump size decides whether they work. Above-ground pools often run small cartridge pumps. The Intex mat publishes a ceiling (1/3 HP, under 2,000 gal/hr). The SunHeater listing says it uses your existing filtration and includes flex-hose fittings for rigid-wall pools, and that hard-plumbed installs need extra parts. Floats need no pump at all.

Two rules that hold for every plumbed option: route the flow through the collector only while the sun is on it, because a collector at night radiates heat away; and put the collector as close to the pool and as low as practical, because every foot of hose and height costs flow.

Everything above is sized for a pool of a few thousand gallons. If yours is inground, the equivalent products are rigid panel arrays measured in hundreds of square feet — see solar panels for inground pools.

The purchase that matters more than any heater

A small pool gains heat faster than a big one and loses it faster too. Every solar heater on this page stops working at sunset, and the pool carries on losing heat until sunrise. A cover on the water overnight is what turns a day’s solar gain into a warmer morning instead of a wasted afternoon. The above-ground cover picks are here, and if you are still deciding between solar and a powered heater, the full above-ground heater comparison puts every type side by side.

The order to buy in

1. A cover first. Then measure the overnight drop at dusk and dawn. If it is small, you may not need a heater at all.
2. Check your pump against the product before buying any plumbed collector.
3. Size by area. Work out your pool’s surface and aim for collector at 50 to 100% of it — or coverage near 80% for floats.
4. Buy the product that gets you nearest that number for the space and money you have, and expect to add to it.