How to pick a pool heater: gas, heat pump, or solar

What are the three types of pool heaters?

Almost every pool heater sold is one of three kinds, and they do not compete on quality so much as on how they make heat. A gas heater burns natural gas or propane to heat water as it passes through, the way a furnace works. A heat pump uses electricity to move heat out of the outside air and into the water, the same trick a refrigerator or an air conditioner uses, run in reverse. A solar heater pumps your pool water up through panels in the sun and lets the sun do the heating for free.

That one difference in how they make heat drives everything else: how fast they warm the water, how much they cost to run, whether cold or cloudy weather stops them, and how long they last. Get the type right for your situation and the rest is sizing. Get it wrong and you end up with the pool heater a lot of owners regret, either paying a gas bill to maintain a temperature a heat pump could have held cheaply, or fighting a heat pump that cannot warm cold water on the exact spring weekend you wanted to swim.

Which pool heater brands and models should you look at?

A handful of names make up most of what gets installed, and within each type the units are more alike than the marketing suggests, so it is fine to pick by type first and shop the reputable brands second. The table below groups the common choices by the three types.

A note on the high-efficiency tier: there is a separate class of condensing gas heaters, such as the Pentair ETi 400, that reach about 96 percent efficiency by pulling extra heat out of the exhaust before it vents. They cost more up front and make the most sense where gas is expensive and you run the heater a lot. For most owners a standard 82 to 84 percent unit is the value pick, and the money is better spent on a cover and correct sizing.

Gas vs heat pump pool heater: which is better?

This is the real fork for most in-ground pools, and the answer is that they are good at opposite things. A gas heater has the muscle to raise water temperature in any weather and to do it quickly, so it can take a cold pool and make it swimmable in an afternoon, or hold a spa at 102 degrees on demand. A heat pump cannot match that. It adds heat slowly, closer to a degree or so an hour in good conditions, and it leans entirely on the outside air being warm enough to pull heat from.

Where the heat pump wins is the bill. Because it moves heat instead of burning fuel to make it, the Department of Energy rates heat pump pool heaters at a coefficient of performance between 3 and 7, meaning three to seven units of heat delivered for every unit of electricity it draws. A gas heater, by contrast, is spending fuel the whole time it runs. Over a full season of keeping a pool warm, that gap is large, and owners who swim often in a mild climate routinely say the heat pump pays back its higher purchase price within a few years and then keeps saving.

So the deciding questions are how often you run the heater and how cold it gets when you want to swim. If you maintain a comfortable temperature across a long season, the heat pump's low running cost dominates. If you heat the pool only for the occasional nice weekend, or you push the season into cold months, gas is the practical pick because it does not care about the air temperature and it gets there fast. Plenty of owners in mixed climates end up owning both, a heat pump for cheap everyday warmth and gas for speed and cold-weather backup, precisely because each one fails where the other shines. The running-cost gap between the two is large enough that it is worth seeing in dollars for your own pool before you decide.

How fast does each type heat a pool?

Speed is where gas separates itself, and it is often the thing that decides the purchase once an owner has waited three days for a heat pump to bring a pool up. Heating speed is really just heat going in versus water to be warmed, so it depends on the heater's output against your pool size rather than a fixed rating, but the ranking is consistent.

• Gas is fastest. A large gas heater can raise a pool a couple of degrees an hour and works the same on a cold morning as a warm one, so it is the only type that reliably heats a pool from cold to swimmable in a single afternoon.
• A heat pump is slow and steady. Expect something like a degree to a degree and a half an hour in good conditions, and figure a day or more to bring a freshly opened pool up to temperature. It is built to hold a temperature, not to blast a cold pool warm on short notice.
• Solar is the slowest and depends on the sun. It adds heat gradually over sunny days and does nothing at night or under heavy cloud, so it is about extending your season and holding warmth, never about heating on demand.

The practical takeaway: if the pattern you picture is deciding on Friday that you want a warm pool on Saturday, only gas delivers that. If you keep the pool warm continuously and just want to top it up, the slower types are fine.

What is the cheapest pool heater to run?

In pure running cost the order is clear: solar is cheapest, a heat pump is next, and gas is the most expensive, often by a wide margin. Solar's only real cost is running the pump that is already circulating your water, so day to day it is close to free. A heat pump's high efficiency keeps its electricity use low. A gas heater burns fuel continuously while it runs, and propane in particular delivers the monthly sticker shock that shows up most in owner complaints.

Two things bend that ranking, though. The first is climate: a heat pump only stays cheap while the air is warm enough to work well, and a solar system only earns its keep where there is real sun. The second is how much heating you actually do. A gas heater fired up a handful of times a season can cost less overall than a heat pump running constantly, which is part of why occasional-use owners still choose gas. Exact dollars depend on your fuel rates, your pool size, and your target temperature, so it is worth running the numbers for your own pool rather than trusting a generic figure.

Which pool heater is best for cold climates?

Cold weather is where the heat pump falls down, and it is worth being precise about why. A heat pump pulls heat from the outside air, so as the air gets colder there is less heat to pull. The Department of Energy notes heat pumps are most effective when the air stays above roughly 45 to 50 degrees; below that their output and efficiency drop off sharply, and many units stop being practical well before their listed minimum operating temperature near 40 degrees. The cruel part is the timing: the cool, cloudy spring and fall days when you most want to warm a cold pool are exactly when a heat pump has the least air heat to work with.

That is why gas is the answer for cold climates and for stretching the season on either end. It heats regardless of the outdoor temperature and it does it fast, so it can push a pool into the shoulder months when a heat pump simply cannot keep up. If you live somewhere with genuinely mild air through your whole swim season, the heat pump is fine and cheaper to run; if you want to swim when it is cold out, buy gas. Solar in cold weather is a non-starter as a primary heat source, though a solar cover still helps any heater hold its warmth overnight.

Do you need a gas line or a 240V circuit to install one?

Before price, there is a feasibility gate that catches a lot of buyers: each type needs something at the equipment pad, and if you do not already have it, the cost of adding it can dwarf the heater. This is the hidden variable that flips the real total, so check it first.

• Gas heaters need a gas supply of the right size. A pool heater is a big gas appliance, and if your meter or line cannot feed it, running a new line from a distant meter can add a serious chunk to the job. Propane is an option where there is no natural gas, but then you are buying and storing fuel. Gas installs also involve venting and clearances and are permitted work, so this is a licensed-installer job, not a weekend project.
• Heat pumps need a dedicated 240V circuit. A typical unit wants its own 240V circuit on a 50 to 60 amp breaker, and if your panel cannot spare that, a panel or service upgrade is a real added cost, especially on an older home that already has an electric vehicle charger or electric heat on the panel. The heater is the easy part; the circuit is where an electrician's bill lands.
• Solar needs suitable, sunny roof or ground space. The collectors have to go somewhere that faces the sun, and the amount of space they need is set by your pool, so a shaded or wrong-facing roof can rule solar out before cost even enters the picture.

One safety point that applies to every type: your installer has to bond the heater into the pool's electrical bonding grid, a code requirement that ties all the metal parts together to prevent stray-voltage shock. It is not optional and not a do-it-yourself step, so confirm the installer handles it.

How long does a pool heater last?

Lifespan is a genuine buying lever, because a cheaper heater that you replace twice as often is not actually cheaper. The Department of Energy pegs the average gas-fired pool heater around 11 years, and gas heaters tend to sit at the shorter end of the range, with water chemistry and lack of maintenance shortening them further. Heat pumps generally run 10 to 15 years or more, helped by having fewer parts in constant contact with pool water and combustion. Solar collectors last the longest, commonly 10 to 20 years, since there is little to wear out.

Put lifespan together with running cost and the long-term picture shifts toward the electric and solar options. A gas heater keeps billing you every month it runs and gets replaced sooner; a heat pump or solar system costs more up front but spreads that cost over more years of much cheaper heat. That is the case for paying more at the outset if your climate suits it, and the case for gas when you value speed and all-weather certainty over the monthly bill.

Natural gas vs propane pool heater

If you have landed on a gas heater, the fuel is its own decision, and it mostly comes down to what is available. The same heater can usually be ordered for either fuel, so performance is similar; the difference is cost and hassle. Natural gas arrives by pipe, is generally cheaper per unit of heat, and you never think about supply. Propane is delivered and stored in a tank, tends to cost more to run, and means keeping an eye on the tank level, but it is the way to run a gas heater where there is no natural gas line.

One modern detail worth knowing: any new gas pool heater uses electronic ignition rather than a constant-burning pilot light, so it is not quietly wasting fuel between swims the way old units did. That is a federal efficiency requirement, not a premium feature, so you get it on any current heater regardless of brand.

Are pool heaters getting more efficient by law?

Federal efficiency rules do apply to pool heaters, and it is easy to find the details stated wrong, so the current picture is worth getting straight. A gas pool heater sold today must meet a minimum thermal efficiency of 82 percent and cannot use a constant-burning pilot light. In practice the mainstream units most people buy, the familiar Pentair, Raypak, Hayward, and Jandy models, land around 82 to 84 percent, while a separate tier of high-efficiency condensing heaters reaches into the mid-90s at a higher price.

A newer standard finalized in 2023 raises the gas minimum to 84 percent and, for the first time, sets an efficiency floor for electric pool heaters strict enough that it effectively requires heat pump technology. That standard does not take effect until 2028, so it does not change what is on the shelf right now, but it is the direction things are heading: toward a higher gas floor and away from plain electric-resistance heaters.

What is the best pool heater for an above ground pool?

Above ground pools change the math in two ways. They hold far less water, so they need a much smaller heater than an in-ground pool, but their thin, exposed walls lose heat quickly, which is why owners treat a solar cover as close to mandatory alongside whatever heater they choose. All three types come in above-ground-friendly sizes, but the mix leans different here, driven by cost and by the fact that an above ground pool is often semi-temporary, so buyers resist a permanent gas-line install.

• A compact heat pump is the well-liked serious option. For a larger above ground pool such as a 24-foot round, owners land on a mini heat pump like the Hayward HeatPro and are generally happy with it for a warm-season stretch, accepting the slow ramp in exchange for a low running cost.
• Small gas is for fast heat and cold snaps. If you swim only on nice weekends and want the water warm today, a small gas heater like the Raypak 156A does it, at the cost of the fuel and, usually, a propane tank.
• Solar options are the budget entry point. Solar dome and coil heaters and flat solar mats are cheap and run on your existing pump, but set expectations: a single dome typically adds only a few degrees over several days, which makes it a supplement rather than a real heater. Larger flat mats do more than domes but still work gradually.

There is one catch specific to above ground setups. These pools often run smaller pumps and hose connections rather than rigid plumbing, and heaters have a flow range they need to sit inside. A heat pump in particular can require something like 30 to 75 gallons per minute, and running outside that window can damage the unit and void the warranty, so a bypass to control how much water goes through the heater is sometimes necessary. Check your pump's flow and the heater's requirement before you buy.

What size pool heater do I need?

Sizing is its own job, and it depends on your pool's surface area, how much you want to raise the temperature, and how exposed the pool is to wind and cool nights. Rather than reproduce the math here, use the pool heater sizing calculator, which takes your pool dimensions and gives you the BTU size for gas, heat pump, and solar, along with a heat-up time and a monthly running cost for each. Pick the type here, then size it there.

The one accessory that helps every pool heater

Whatever you buy, a solar cover is the cheapest thing you can add and the one owners bring up most often. A pool loses most of its heat to evaporation off the surface, and a cover is a lid that stops it, so it holds overnight the warmth your heater put in during the day. That saves fuel or electricity on every type, and with a slow heat pump it is nearly essential, because otherwise the pool sheds overnight much of what the heat pump spent all day adding. It does not replace a heater, but it makes any heater work less, and a thicker reflective cover holds the most heat. Before you agonize over heater types, plan on a cover either way.