Gas Hot Tub Heaters versus Electric Hot Tub Heaters

Back in the early days of hot tubbing, gas-powered hot tub heaters were always less expensive to operate than their electric counterparts. However, with gas prices steadily increasing year after year while the cost of electricity has remained relatively regulated, this simply is not always true anymore.

To make an educated decision about which strategy is best in your situation, you should do a cost analysis of each heating source – something we’ve helped many of our customers do. Surprisingly many of those analyses have revealed electricity to be the less costly of the two forms of energy. You know that this is obviously an unbiased recommendation since we sell both gas and electric heaters – especially since the gas heaters are nearly twice the price of the electric heaters!

Another consideration to take into account when looking at a natural gas or propane hot tub heater is your climate. Many gas heaters are only rated for outdoor use down to 40 degrees Fahrenheit, and none of the ones we’ve seen are rated for use below freezing. Many dealers won’t bother to tell their customers this, and instead sell them replacement parts when their gas heater rusts out prematurely. The only way to run a gas heater during the winter in a freezing climate is to install it indoors, which requires the purchase and installation of both a flue and an indoor heater hood.

In many cases gas hot tub heaters are more costly to buy, to install, and most important, to operate. Make sure to do a thorough examination of your situation before making a choice as to which is best for you.

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24 Responses to “Gas Hot Tub Heaters versus Electric Hot Tub Heaters”

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  2. Dedra Q says:

    I heard that gas heated hot tubs were dangerous due to possibility of burning someone’s skin. Is this true? If so, is there a way to prevent it?

  3. admin says:

    Hi Dedra, and thanks for the question!

    All heaters, gas or electric, are designed to keep from making “cannibal soup”!

    Seriously, though, properly operating you shouldn’t even be able to turn up the temperature on a heater to the point of scalding. By law and design, hot tub heaters should be incapable of exceeding 104 F, considered by the industry to be the maximum safe bathing temperature.

    Of course, a heater’s thermostat can malfunction, but that’s true of both gas and electric heaters. It’s always best to dip a toe first, just to make sure before you immerse yourself completely in your hot tub. Runaway conditions (high temperature) are still very rare, because the heater’s thermostat also has a high limit switch backing it up. It’s more common for the heater to completely fail to heat the water, but that’s still a good reason to dip a toe first, lest you jump into a freezing cold tub!

    Since you asked about gas heaters for hot tubs, this seems like as good a place as any to mention a disturbing trend that we’ve noticed, and that’s people installing and operating gas fired hot tub heaters outdoors in a freezing climate.

    The gas fired heaters we normally sell are rated for operation down to only about freezing, which is about the best that you’ll find. Some other brands are only good down to 40 F.

    We’re often amazed by how few of our competitors are aware of this fact and will freely sell gas heaters to customers for outdoor use in freezing climates. If you intend to install the heater outdoors in a northern climate, you’re required not to use it during the winter if you want it to last. The alternatives would be to install a gas heater indoors (and endure the expense of a necessary flue) or switch to an electric heater.

    Contrary to popular belief, switching to an electric heater might not increase your cost of operation, and we can help our customers to determine whether or not it does based on their per unit costs are for each type of energy.

    Please let us know if there’s anything else we can do to help you, or any other questions we can answer, and thanks again for the comment!

  4. plumbing says:

    For people concerned about the bottom line, it tends to be cheaper to operate a gas stove, depending on the type of gas used to fuel it and the prevailing prices for gas. Gas stoves tend to be a bit more expensive to buy and install, but people may feel that this is worth it when viewing costs in the long term.

  5. admin says:

    Hi, and thanks for the comment! While it used to be true that a gas heater would cost less to operate over the lifetime of the tub with the currently rising oil prices that’s not always the case anymore. We’re always on hand to do a cost comparison for our customers, to make sure they’ll get the most out of their money.

  6. Shawn says:

    I have read that gas heaters heat the tub much faster than electric, and so the tub can be kept at a more economical “mainenance temp”, and brought to “tubbing temp” on demand much easier while electric heaters heat slower, and thus must be kept closer to “tubbing temp” at all times unless you want to wait forever before hopping in every time.

  7. admin says:

    It sounds to me like whoever told you that was just trying to sell you a more expensive heater. Either that, or they didn’t consider the science.

    It takes the same amount of energy to increase the temperature of the hot tub whether it’s done all at once or a little bit at a time. If a tub loses four degrees per day, for example, then you’re heating the water four degrees per day regardless of whether you’re doing it each day or at the end of several days.

    Considering the fact that gas heaters cost twice as much as electric heaters, are more costly and difficult to install, and in many cases are actually more expensive to operate, it hardly seems like a good idea to use one in most cases.

    Since it costs nearly the same energy to heat the tub continuously as it does to allow it to cool for several days only to have to apply the same heat anyway to bring it back up to temperature, why not use the electric heater and have the tub ready for use just about any time you want to use it?

  8. Very infomative post. I was not familiar with Gas & Electric Hot Tub Heaters, so just learned some valuable information, thanks.

  9. fisher says:

    hi,
    In Boston gas is low in cost electric is high ($ .19 KWH ) my plan is to put Hayward 100,000 btu gas heater in series with the electric heater plumbing .
    The elect pump is on continously so the water will not freeze when it flows trru the gas heater placed outside but close to the spa . I intend to insulate any exposed hoses and the gas heater its self . I know the heater is not supp[osed to be used below 40 degrees but the circulsting heatec water will keep the temo above 40.

  10. admin says:

    Hi Fisher. Is there any way you can install the gas heater indoors? Even with the warmed water running through it, there’s a good chance it will rust out prematurely being operated in a climate such a Boston’s winters. You’ll likely end up having to buy a new heater within 5 years.

    As for saving energy, yes, your electrical rates are indeed rather high, and it is true that all the “hydrofracking” going on has created a glutted market for natural gas in the last couple of years, but all this might be temporary.

    Even at current rates, you need to calculate how long it will take in energy savings to pay for that expensive gas heater. You may discover that it will take longer to save enough to pay for the heater than the heater’s expected life span, even assuming an indoor installation and no concern for premature corrosion.

    By the way, what’s the point of having the electric heater, too? If it’s so that you won’t have to run the gas heater in the winter, we can understand that, but then it begs the question as to why not simply install just an electric heater and leave it at that?

    If you’d like to contact us via e-mail, we can send you an energy guide that will help you to calculate an estimate of just how much money you’ll save using the gas heater.

  11. sandra says:

    In Hawaii our propane is $6.00 a gallon while our electricity is .45 cents a kilowatt. Either way you cut it, it is very expensive to run a hot tub but I’m not sure that running the heat for hours every day as opposed to turning on the gas only when you want to heat it up makes much sense. If the tub is used irregularly it makes more sense to use gas; which heats up in 30 minutes as opposed to electric which takes 3 hours to heat up the same amount of water. So what I’m learning is that electric heaters are meant to run for hours a day with the circulating pump and have a cover that keeps in the heat where as the gas heaters are meant to use on demand. So it will depend on the usage as to which one makes more sense. The question now is where to have a hard cover made since we put in electric before realizing all of the above.

  12. admin says:

    Hi Sandra! That’s an excellent question and the short answer is, you can get a custom cover from us! We’ll build you a cover to your exact dimensions for the same price as you could get a “cookie cutter” cover somewhere else. For these covers and options pleas see http://www.almostheaven.net/aho/covers.htm. In fact, it’s such a good question, we decided to make it into our very next blog post. If you’d like to read the long answer, and see the post you inspired, please see http://blog.almostheaven.net/heater-differences-and-hot-tub-covers/. Thanks!

  13. tony says:

    I have an outdoor spa witch approx. 3500 litres I would like to know what size heater will I need I would like to use electric

  14. admin says:

    Hi Tony. Thank you for your comment. I’m going to forward your request to one of our technicians who will be able to help you determine the correct heater sizing. He’ll be e-mailing you directly. If you don’t hear from him soon please e-mail us at sales@almostheaven.net. Thank you!

  15. David says:

    What kind of safety is required on an electric heater to avoid getting electrocuted if an element shorts out and you’re In
    the water.

  16. admin says:

    Hi David, thanks for your comment. Electric heaters are required by the National Electrical Code to be connected to a GFCI (Ground Fault Circuit Interrupter), and that will prevent even the slightest leakage of electrical current into the water, making it completely safe regardless of any malfunction. Please let us know if you need any other information!

  17. Don Poindexter says:

    I am about to replace a 30+year old gas heated spa. We like to exercise or just soak in 75 degree water on a hot day and sometimes want the temperature as high as 95 to 100 degrees that evening. Also we sometimes don’t use the spa as long as 30 days at a time and then decide to use it in the next 30 minutes. Aren’t we pretty well relegated to a quick response gas heater?

  18. admin says:

    Your unusual situation is one of the few that does indeed call for a gas fired heater, given the fact that your heat rise with even a relatively small 125,000 BTU gas heater is nearly triple that of the largest electric heater (i.e. 11 kW).

    For others, their cost of electricity is so high that they can save money on their daily operating expense by installing a natural gas heater. A comparison of per unit energy costs will reveal roughly how long it will take to make up the higher cost of the gas heater as compared to the electric heater, and we can help you with those calculations.

    Just keep in mind that there is no gas heater that’s meant to be operated outdoors in freezing weather. If you need to operate a gas heater in freezing weather it should be installed indoors and connected to a flue. Otherwise, condensation will corrode the heater prematurely from the inside out!

  19. Gordon says:

    I have a large 12 x 8 swim spa. It is indoors in its own sealed off room. My electric cost for the house are running 160 a month. With Natural Gas being cheap now days I am considering gas heater. I have not read anything that addresses the chemicals in the water and the affect on heating elements. I dont have to be concerned about outside temps. Can this be done? Direction Please

  20. admin says:

    Hi Gordon. Thanks for your comment. I’ve emailed you directly, and you should be hearing from a salesperson shortly to discuss your specific situation. Please let us know if you need anything else!

  21. Valerie in Chicagoland says:

    I’ve been reading these comments as I’m about to have to replace my “outdoor” gas 50,000 btu Raypak spa heater. I’ve had my redwood hot tub for 30 years..gone thru 2 Teledyne lars gas heaters and now on my first Raypak. The Teledyne Lars lasted about 7 years each…My Raypak is still going at over 3 years. These gas heaters are installed “outside” in freezing weather all year for 30 years, never had a problem…I run my tub 24 hours a day to keep the PVC pipe from freezing outside the porch in the winter and in the summer run it about 2 hours per day to keep the temp up in case I want to use it. Now I find I can’t find a 50,000 but gas heater, so afraid I may have to go electric, which will take much longer to heat up the tub as I use it when I’m in the mood, so need to heat it up in about an hour or two from 15 to 20 degrees down…electric just can’t do it.

  22. admin says:

    Hi Valerie!

    Thanks for your comment. First of all, if you’re happy with something that costs that much lasting only seven years, you don’t have high enough standards! If you had started with an electric heater 30 years ago, it might actually still be operational, albeit having had a $50 part or two replaced over the years. Ever have to pay for a part for a gas heater? Some of them cost more than an entire electric heater.

    Actually, if you had installed your gas heater indoors and connected it to a flue, even it might still be operational. There’s a good reason that you’ll likely find a warning in the heater’s manual about frequent operation at below freezing temperatures.

    Moreover, depending upon how well insulated your tub is and how often you use it, it might not take any more BTUs to keep the tub up to temperature at all times than it does to let it cool and be reheated time after time. You’re likely to be regaining the same amount of lost heat either way. Then the decidedly quicker heat up time of the gas heater offers no benefit, plus the tub is always ready for use.

    To be fair, there often is an issue regarding cost of electric versus natural gas, and that’s due to the current glut of natural gas on the market. In places such as California where electric rates are ridiculously high, significant savings can be seen by using natural gas, even enough to make it worth spending an extra thousand dollars or more on a heater that only lasts seven years.

    Propane will always be more expensive than electric, but the cost of natural gas has risen and fallen sharply over the last 30 or 40 years, and right now it’s routinely less expensive than heating with electricity unless your cost of electricity is a real bargain.

    However, although natural gas prices are at historic lows due to fracking, they’re working on ways to export it, and it’s being pushed for automobiles and power generation. Such increases in demand can only increase its cost.

    On top of that, many in the scientific community consider estimates by the wildcatters of how much natural gas is available through fracking to be wildly optimistic. A gas well drilled through normal means tails off its production, but a fracked well shuts off like a switch when it’s depleted.

    So for all we know, electric could be back to being a better deal than natural gas sooner than you think and even before it can pay back the difference in costs between purchasing and installing an electric heater versus a gas heater.

    No such decision can properly be made without at least comparing your present costs of electricity and natural gas, and while it’s difficult sometimes to say how many BTUs a new tub installation needs to stay heated since it depends on location, season, etc., it’s quite easy to compare cost per each BTU generated through gas versus electric.

    And for someone with an existing tub that might already have a handle on how much gas or electricity they presently use, it would be easy enough to determine the added costs or savings from switching energy sources.

    We’re always happy to help our customers with such calculations, so feel free to ask.

  23. bert says:

    I am researching gas hot tub heaters for a very different reason. I am building an off grid house. I have plenty of electricity for the house. I have always had a grid tied hot tub at my house in town and all though everyone thinks that electric hot tubs are cheap to run, when you produce your own electricity, they are not. I have only enough electricity for a circulation pump, not to heat. I plan to do a “partial” heat with a solar thermal panel and need a heater to boost the heat. I have run a propane gas line to the tub site, all outdoors although covered from weather. My question is: I live at 7500 feet in elevation in Colorado. It certainly gets below freezing. will the external heater actually freeze, meaning the water that is in it, if so is there a way to stop cock the out flow and drain the heater at night? I don’t have many options, just need to think creatively. thanks.

  24. admin says:

    Hi Bert! Thanks for your comment and great questions.

    I sent them to one of our technicians, and he responded as follows:

    “The concern is not that the water in the heater might freeze. If you had to worry about that, you’d also have to worry about the water freezing in the pump, the filter, the piping, etc.

    Any outdoor tub system must have some sort of freeze protection system. As long as you have power to circulate the water when it drops below a certain temperature, then freezing is not the issue.

    The issue is condensation and corrosion. The reason that you can’t subject a gas heater to freezing temperatures when it’s running is because you will cause condensation to form inside the heater, and this condensation will eventually corrode the heater from the inside out. The process generally takes less than ten years and sometimes less than five years in very cold and humid environments.

    The solution, if you can manage it, would be to install the heater in an heated indoor space and connect it to a flue, then run your piping from there out to the tub. If you want the heater to last and plan to use it through the winter, this is really your only solution.

    Installing the pump and filter indoors too also serves the purpose of saving energy and mitigates the most expensive form of freeze damage in the case of a catastrophic freeze to the system, such as if you ran out of power and couldn’t keep the water circulating.”

    I’m also going to send his comments to the email address you provided. Please let me know if we can do anything to help!

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