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Thread: Cost to heat pool.

  1. #1
    Join Date
    Jul 2006

    Default Cost to heat pool.

    Does anyone have an easy way to figure out what it will cost to heat your pool? I am in the design stages of my pool.
    The pool will be about 475sf surface area and about 15k-17k gals.
    The hot tub will be about 25sf and about 800 gals.

    I am not really sure how the tub and the pool plumb together to heat but I know it works somehow.

    P.S. I live in the Phoenix AZ area.

  2. #2
    mkelley is offline Registered+ Thread Analyst mkelley 0
    Join Date
    Jun 2006

    Default Re: Cost to heat pool.

    Sure -- it's quite easy. It will cost you absolutely zero to heat your pool... after you install solar.

    Trust me, there is absolutely no other way to go (I know -- I spent $1K heating our pool for a month and I learned my lesson). I would *never* use gas heat, except for the spa (even there the solar will help -- our solar can get the spa up to the 90's and then it's only pennies to push it to 102 or so).

    Actually understanding how your pool will heat has to do with surface area, the amount of sun it gets, whether it's sheltered from the wind, etc. All of these calculations will tell you how many solar panels you will need (once again -- you *will* want solar, and you will want to calculate the panels properly). There are many solar sites that will do this for you after you answer the questions.

    No matter how you cut it, no matter where you live or how long a season you're looking for, solar will pay for itself (ROI) in five years or less. With energy costs the way they are, there is no excuse to go any other way.

  3. #3
    Join Date
    Dec 2004
    Sacramento, CA, USA.

    Default Re: Cost to heat pool.

    There are many factors in what it costs to heat the water in the pool or spa.

    What you are probably asking is, "How much will my heater cost to run?"

    A 400k BTU heater will use that much in gas in one hour. Most utility companies charge by the therm for natural gas. There are approximately 100K BTU in a therm. You can do the math from there. Find out what your company charges per therm and multiply it by 4 and you will get the approximate hourly cost. You can contact your utility and they an give more precise figures, but since you don't ever know exactly how much water you have in a pool, and the amount of energy in a therm can vary depending on supply, these figures are close enough.

    If you are using propane, there are about 100K BTU in a gallon, so a 400K heater will use about 4 gallons per hour.

    A 15000 gallon pool will have about 120,000 pounds of water in it. It takes 1 BTU to heat 1 pound of water 1 degree. A 400K heater, at modern efficiencies will put about 320K BTU into the water, more or less. It should be able to heat 15000 gallons about 3 degrees per hour. This does not take into account any heat loss from the surface of the pool.

    In warmer weather, most spas will heat to 100 degrees plus in about 10 to 15 minutes or less with a 400k heater. In colder weather (do you have that in AZ?) maybe 20 minutes.

  4. #4
    leejp is offline Registered+ Weir Watcher leejp 0
    Join Date
    Dec 1969
    Upstate, NY (Dutchess County)

    Default Cool your house and heat your pool..

    In the Northeast there are many days in the early and late summer (May - mid June, Mid-August - September) where the pool's too cold to swim in but the home AC is running all day long. Typically the outside temp in the high 70s to mid 80s during the day and high 60s to low 70s at night. If there's any humidity the home AC runs.

    One should be able to dump the heat from the house into the pool with a simple refrigerant to water heat exchanger and and essentially lower home cooling costs and get free pool heating at the same time.

    I've found very little in the way of a pre-packaged unit to do this but here's a guy in the DC area selling services/equipment.


    Not sure if this will work in AZ. I know that since it's dry that it can be very comfortable without AC even at higher temps.
    26,000 Vynil Liner L Inground
    Hayward 1HP Superpump + Hayward Pro Grid 4800 DE Filter
    Poolvergnuegen thepoolcleaner Pressure Side Cleaner
    Loop-Loc Mesh cover

  5. #5
    Join Date
    Dec 1969
    Fortson, Georgia

    Default Re: Cost to heat pool.

    Solar is definately less expensive in the long run if you have the solar exposure (I assume you do in Arizona) and you don't mind the looks of the panels. My pool is tucked in among the trees and we get less than an hour of full direct sun per day on our pool. Used solar for five years, but the wife was always complaining about the panel (didn't want it on the roof or patio, and it would kill the grass). So I got rid of her -- the solar panel, not the wife! Installed an electric heat pump last week. Pool temp jumped 12 degrees the first 24 hours! It works like an air conditioner, only backwards. Blows cool air out and puts warm water into my pool. That guy in DC may be on to something. I've been thinking the past couple of days it would be nice if I could harness that cool air and get it into my house. Guess it's too late to convince the wife that the ducting would look good ;-)

    Good luck

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