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Thread: Is my heater/hr cost math correct?

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    Is my heater/hr cost math correct?

    My last NM Gas bill last month was for $158.42 and I used 220 therms.
    If my math is correct, that brings my cost per therm to $0.72.

    Today, the gas company switched the meter and I ran my 400K Pentair heater for exactly an hour with nothing else in the house.
    I see that I used about 3200 Cubic feet, which translates to 32 therms, according to this site: http://www.kylesconverter.com/energy...of-natural-gas

    32 therms for one hour at cost of $0.72 per therm, equals roughly $23.

    The pool heater ran for 5 hours to bring the brand new pool's water from 69 up to 80, which is roughly 2 per hour.

    Is my math correct that this 5 hour run will cost me roughly $100 ?!?
    Viking fiberglass Island Breeze II (16'x40'x8'); Pentair pump/filter/heater/chlorinator; IntelliTouch with iX+3; Autelis.

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    mas985's Avatar
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    Re: Is my heater/hr cost math correct?

    A 400k BTU heater uses about 4 therms per hour. Maybe you are not reading the meter correctly.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Is my heater/hr cost math correct?

    Quote Originally Posted by mas985 View Post
    A 400k BTU heater uses about 4 therms per hour. Maybe you are not reading the meter correctly.
    I hope you're right, but take a look at my starting point reading:

    and one at my 1 hour mark:




    I just looked again, end of the day after heater ran 4-5 hours, and I'm at ~10,700 cubic feet, if I'm looking at this correctly.
    Viking fiberglass Island Breeze II (16'x40'x8'); Pentair pump/filter/heater/chlorinator; IntelliTouch with iX+3; Autelis.

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    mas985's Avatar
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    Re: Is my heater/hr cost math correct?

    Each dial is per revolution. The last dial on the right is 1000 cu-ft per revolution or 100 cu-ft per number increment. So that is about 320 cu-ft which is 3.2 therms. But again, the heater should be using about 4 therms but it is possible the gas line is not big enough which can limit the burner rate.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Is my heater/hr cost math correct?

    Gotcha; thanks.
    I thought it was like a tach in the vehicle, where the dial is a single digit indicator and the multiplier is displayed above/below.

    So today's run was not 100 bucks -- it was only $10. That's great news and a reason to run the heater to get the pool up to temp.

    Speaking of which, what's a good temperature to keep the pool at for a bunch of kids playing around and good 'ol me swimming laps.
    I must say that I'm usually on the cold side and am easily spotted in the crowd of t shirt wearing people as the one in a sweater.
    Viking fiberglass Island Breeze II (16'x40'x8'); Pentair pump/filter/heater/chlorinator; IntelliTouch with iX+3; Autelis.

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    JasonLion's Avatar
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    Re: Is my heater/hr cost math correct?

    There are no absolute guidelines for water temperature, as it involves a lot of personal preference. Still something in the 78 degree range is often good for people who are being very active. The less active you are, the warmer you will want the water. Air temperature also enters into it, as getting into a cool pool from cool air can be difficult for many people.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Is my heater/hr cost math correct?

    Kids will swim in anything no matter what the temp is of the water. Unless there is ice on it.
    Paul
    http://www.gastekservices.com A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Re: Is my heater/hr cost math correct?

    Quote Originally Posted by ps0303 View Post
    Kids will swim in anything no matter what the temp is of the water. Unless there is ice on it.
    Paul, you've got that right.

    My pool was set on Feb. 9th. The temperature during the day was in the 40s.



    My daugher didn't get home until after 6PM. I'm guessing air temperature was in the 30s, with water (coming from 683' deep well) in the 50s.
    You should have seen her mom trying to talk my 9 year old out of going in



    Viking fiberglass Island Breeze II (16'x40'x8'); Pentair pump/filter/heater/chlorinator; IntelliTouch with iX+3; Autelis.

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    Re: Is my heater/hr cost math correct?

    Yes Mario, there is 100,000BTU in every therm. Your hearted is a 400K unit. (400,000 BTU). The max the unit will run thru it is 4 therms an hour.
    17K Gallons, Gunite & plaster, Hayward Ecostar VS, AquaCal SQ110, Ecofilter E5 (Zeolite), Pentair in line chlorinator, ProLogic P4 automation. Bought home in 2015. Very large caged in pool in Fort Myers.

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    Re: Is my heater/hr cost math correct?

    Hi Mario.
    If your heater is like mine, it's been adjusted for the higher elevation. From my Raypak 409 manual:
    Reduce input 4% for each 1000 feet above sea level when installed above 2000 feet elevation
    400K BTU * 0.88 = 352K BTU input

    I think the heater efficiency was around 80-82%.

    I get around a 1F rise every 2 mins for my hot tub. I used to think that was crappy but after doing the math tonight - it's pretty close.
    20K gal 16x32' gunite pool and 7' spa / Pentair Intelliflo VS (pool) and WhisperFlo 3HP (spa) pumps / Pentair CC320 cartridge filter / Raypak 406A heater / EasyTouch 4 controller / CoverPool T-3 cover

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