Gas Pool Heaters: How Do They Work?

the woman touches the gloss of the water with her hand

Charlie Hardcastle

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Many homeowners find choosing a pool heating system to be one of the most confusing decisions in the world. Even though a lot of people are now making the switch to solar heaters, there are still those that continue to benefit from gas heaters. So, the question most people ask is what the difference really is? How does a gas pool heater work, and what makes it perhaps better than an electric or solar heater?

In this article, we’ll answer these and other questions to help you make the perfect decision based on the conditions where you live. We’ll address the advantages and disadvantages of various pool heating technologies when compared to gas heaters.

How Does A Gas Pool Heater Work?

As the name suggests, a gas pool heater burns gas or liquid propane to heat the water. Similar to a gas geyser, the fuel burns in a combustion chamber. The swimming pool water is then run through a series of copper coils that go through the combustion chamber where the water is heated. As the gas continues to burn, there is a consistent flow of pool water through the copper coils that returns to the swimming pool, consequently warming it up.

As a rule of thumb, a larger unit will heat a swimming pool sooner than a comparatively smaller one. However, a small gas pool heater will take longer to heat a large swimming pool. That’s why you will want to buy a size that matches your needs exactly. Most swimming pool heater technicians should be able to offer a size recommendation if you are not sure which one will work out best for you.

The exhaust fumes created from burning the fuel are mainly CO2 and a few other gases. That’s one of the reasons why the combustion chamber needs to be well ventilated, and it is also why environmentalists deem this pool heating technology as “polluting” to the environment.

Who Needs A Pool Heater?

In a nutshell, anyone who needs to heat their pool to avoid hypothermia during their daily swim will need a pool heater. The common misconception is that only people living in colder states like New York, Washington, etc., will need a pool heater. However, like all misconceptions, the assumption is rooted not in facts but in gut feeling.

Even states like Florida and Texas can get pretty cold during the winter. Sure, the pool water will not kill you, but it could certainly make you sick. So, while you may not need to run the pool heater all year round in these states, they are still often needed.

In states where it tends to get cold sooner, having a pool heater will mean being able to use your pool for a little longer than would otherwise be possible. However, a gas pool heater coupled with an insulating cover can help keep your pool water warm even when it’s near freezing outside.

Cost Of Running A Gas Swimming Pool Heater

The cost of running a gas swimming pool heater varies considerably. It primarily depends on the amount of energy needed to heat the water given the outside temperature and your local utility rates. A 400,000 BTU gas swimming pool heater uses around 4 therms per hour to heat water. The National Average Price for Natural Gas is $2.20 per gallon, so for one hour of use, you will spend approximately $9.00. The efficiency of a gas heater will also depend on whether you use a pool cover.

On average, a gas pool heater costs $200 to $400 per month, while an electric one may cost $120 to $200. While both types of heaters work effectively, the latter is less convenient and more difficult to install. Gas pool heaters are generally cheaper upfront and easier to maintain.

The Efficiency Of A Gas Swimming Pool Heater

Among the different types of pool heaters, gas units have undergone the most development in the past thirty years. Since the introduction of millivolt electronic ignition, gas pool heaters have become more efficient. Though mind you, they still aren’t the most efficient. 

In other words, they now consume less fuel than traditional pilot igniters, which can reduce your utility bill significantly. However, it would help if you also considered the operating costs of a gas swimming pool heater before buying one, depending on where you live, especially since gas prices have gone up exponentially in these past five years alone.

A gas swimming pool heater’s efficiency depends on several factors, one of which is age. The older the unit, the lower its efficiency. Newer models are less energy-intensive and emit fewer emissions than a few years ago. They are also easier to maintain. Speaking of maintenance, maintaining one regularly will help keep its efficiency optimum.

Gas swimming pool heaters also range in size and output. They can produce seventy to four million BTU. The efficiency rating of a modern heater is between eighty to ninety percent, which equals around three-hundred thousand BTU of heat output.

Gas and electric swimming pool heaters differ in cost. Gas models tend to be more expensive upfront if they require running an outdoor gas line. However, they are still often less expensive in the long run when compared to electric units.

Environmental Impact Of A Gas Swimming Pool Heater

While the environmental impact of a gas swimming pool heater may be smaller than an electric model (depending on how your state generates electricity), there are several reasons to choose this type of heating appliance. One of the most significant reasons is that it can heat a pool faster than any other device.

Gas swimming pool heaters work fast and are relatively inexpensive to run, but it does produce greenhouse gases. Because of this, you’ll want to think twice before deciding on a gas model if you are quite an environment-conscious consumer. However, even an electric unit can be responsible for giving out greenhouse gases if the electricity produced comes from coal or fossil fuel burning plants.

Why Should People Choose Gas Pool Heaters?

One of the main reasons to choose a gas swimming pool heater is that they are more efficient when heating your pool within a short period. It can reach the desired temperature quickly and maintain it despite the weather, however freezing cold.

This feature makes it perfect for those who don’t want to run a pool heater every day. It is also easier to find a professional to fix your gas pool heater than any other type of pool heater. Since the technology isn’t as “high-tech” as some other pool heaters, most problems are also comparatively cheaper to address.

The other reason why many homeowners choose a gas pool heater is that they want to replace the existing one with something more efficient. Replacing an old gas heater is far cheaper and easier than replacing it with perhaps an electric heater, which will require a fresh installation with a large upfront cost.

Frequently Asked Questions

What Is The Best Type Of Pool Heater?

There are three basic pool heaters, i.e., solar, heat pump, and gas. These three types of heaters can be installed yourself or by a handyman. The first two types are relatively easy to install, and most are not difficult to use. However, we recommend hiring a professional to install these pool heaters. Which is best depends on what you value most – heat efficiency, energy efficient, or upfront/long-run costs.

How To Choose The Right Size Pool Heater?

First, you need to know the size of the pool. A round pool with a diameter of 30 feet or more requires a gas pool heater with at least 100,000 BTUs. If you want to heat your pool consistently, you can purchase a thermostat to control the temperature. If the pool is for occasional use, you’ll need a larger unit that can rapidly heat the water to the desired temperature.

How Much Does A Gas Pool Heater Cost?

What you pay for a gas pool heater will depend on its make, model, and size. As you’d imagine, larger pool heaters are, on average, more expensive than smaller ones. Also, more renowned brand names are more expensive than lesser-known ones. On average, you can expect to pay between $2000 and $4000 for a gas pool heater backed by a warranty.

What Type Of Ignition Is Best For My Pool?

Most top heaters come with a fireman’s switch. This device helps prevent the heater from being damaged by fire. It works best in conjunction with a pool pump timer and shuts off the heater 15-20 minutes before the system shuts down. The temperature of a gas pool heater is then regulated by a digital thermostat. This type of ignition system is versatile and highly efficient at keeping your pool warm.

Are Gas Heaters Better Than Their Electric Counterparts?

There are several inherent advantages and disadvantages to electric and gas pool heaters. Gas pool heaters are cheaper upfront and have comparatively lower monthly running costs. Electric heaters will work better than gas heaters at maintaining the temperature but will not work as well in frigid temperatures. Gas heaters are best suited for short periods when you need to heat a pool in a hurry. These heaters can also provide a spa-like atmosphere to your property. On the other hand, electric heaters will often need to be run for longer, which translates to a higher electricity bill.

What Disadvantages of A Gas Pool Heater Should I Be Aware Of?

We have gone over the few valuable advantages of a gas pool water heater, but you should be aware of a few disadvantages before buying. For starters, gas pool heaters aren’t as efficient as some competing technologies. The COP of a gas pool heater is between 0.80 and 0.85.

Despite many people looking past the inefficiency of a gas pool heater in the past because of low gas prices, today, that’s not the case. The recent increase in gas prices has meant that the inherent inefficiency of a gas pool heater is increasingly unacceptable for some homeowners.

A few other disadvantages include the harmful effects of exhaust gases on the environment, the requirement of a gas line stretching to the unit in some cases, and its comparatively short lifespan.

What Is A Good Eco-friendly Alternative To A Gas Pool Heater?

If you are looking for a more cost-effective and eco-friendly solution, then an electrical or what’s called a pump heater will probably suit your needs the best. However, since these heaters work by pulling in ambient heat from the atmosphere, they will not be effective in places that freeze over. So, if there isn’t any ambient warm air to heat the water, these heaters will not work very well. That said, they are both eco-friendly and light on the pocket because they don’t rack up a high-power bill, making them perfect for places that do not freeze over.

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