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  1. #1
    Join Date
    Jul 2005
    Location
    SE PA
    Posts
    183

    Operating cost comparison......hot water

    Hope this is the right forum. I have a neighbor with an oil boiler because he has some hot water baseboard heat. Currently his domestic hot water is "driven" by an indirect hot water tank off the boiler.

    Given oil's recent prices, he's considering switching just the domestic hot water to either electric or propane (he has propane at the property for a pool and cooktop in the kitchen).

    Is there a relatively straight forward formula to compare the cost of heating a gal of water for elec vs propane vs oil??? I know oil will generate 140k BTU's per gal, propane 91k btu's per gal, and it takes 3412kWh of electricity to get to one BTU.

    I'd be interested in seeing the formula to compare the costs differences for 1 gal of hot water. If necessary, I'd assume the oil burner at 80%. Not sure what the typical tank electric or propane hot water heater efficiency is.

    Thanks in advance for any feedback.

  2. #2
    Join Date
    Dec 2002
    Posts
    317

    Thumbs up $$$$$

    I just got an "$800" oil bill and i can sympathize Your neighbor should consider a "RINNAI" propane fired Tankless water heater
    you and him should check out the website called "www.foreverhotwater.com" these are very efficient hot water heaters they are available in natural gas and propane.
    as for the boiler if it has a tankless coil in it it is a recipe for more oil consumption. with oil this expensive everyone should have a crown freeport boiler.. Crown Freeport "3" pass heat exchanger low mass cast iron save more $$$$ on oil bill crown freeports are designed to be a "COLD-START" boiler as per the crown reps..

  3. #3
    Join Date
    Mar 2001
    Posts
    1,213
    Have you (he) considered solar? The other issue is the building envelope - upgrade that & you will reduce the heating load substantially. Insulation... you pay once. Fuel you pay forever.

  4. #4
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    http://www.warmair.net/html/fuel_cost_comparisons.htm

    Just enter the cost of each.


    And it is 3.41 btu per watt.
    Karst means cave. So, I search for caves.

  5. #5
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,233
    Quote Originally Posted by im4snow2000 View Post

    Is there a relatively straight forward formula to compare the cost of heating a gal of water for elec vs propane vs oil??? I know oil will generate 140k BTU's per gal, propane 91k btu's per gal, and it
    ... one BTU.

    I'd be interested in seeing the formula to compare the costs differences for 1 gal of hot water. If necessary, I'd assume the oil burner at 80%.
    Cost to heat 100 gallons * 50'F = 41,500 BTU
    $1.96 for electric at $0.15 per kWh
    $1.20 for oil at $3.00 per gallon


    830 lb 50 F = 41,500 BTU

    3,413 Btu/ kw
    12.16 kW
    $0.15 $ /kw
    0.93 Efficiency
    $1.96

    104,000 130,000
    0.8 Efficiency
    0.399 Gal
    $3.00 /gal
    $1.20
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  6. #6
    Join Date
    Sep 2004
    Posts
    654
    Huh?....removing a high efficiency big $$$ indirect hot water maker and install a 'toy' electric element tank instead? Electric is the WORST way to make hot water, your neighbor should be glad he's got what he has already.

  7. #7
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    An indirect water heater will give you almost infinite hot water. An electric water heater will give you hot water for about 30 to 45 minutes and take about 2 hours to recover.

    If your "neighbor" wants to check on the cost, go to the Penn State energy calculator: http://energy.cas.psu.edu/energyselector/

    Or do my version:
    Comparing different heater operating costs:
    1. Choose one or more energy source(s).
    2. Determine the current price of each energy you chose.
    3. Choose two or more different heater models.
    4. Determine the efficiency of each model.

    For each unit:
    5. Multiply the efficiency times the energy’s gross BTUs to determine net BTUs.
    Note: Net BTUs are how much heat you actually get out of the heater.
    6. Divide net BTUs into 1,000,000 to determine how many Units of Measure you need.
    Note: 1,000,000 is just a common denominator, you can use any number you like.
    7. Multiply the Units of Measure times the Energy Cost
    8. Compare the results.

  8. #8
    Join Date
    Sep 2006
    Location
    The depths of hell in PHX AZ
    Posts
    1,140
    Quote Originally Posted by casturbo View Post
    Huh?....removing a high efficiency big $$$ indirect hot water maker and install a 'toy' electric element tank instead? Electric is the WORST way to make hot water, your neighbor should be glad he's got what he has already.
    high efficiency? how is it efficient to burn oil at 3.50 a gallon on an 80 percent boiler??? I'm sorry but my electric is only .10 per kw hour and I'll be joining the ranks of putting an electric HWH back in my house and using it when oil is high and switching to oil IF it ever goes low again. I'm also putting in a high efficiency heat pump too. Don't tell me your like my neighbor and think indirect heaters are FREE because your heating the boiler for heat anyway. LOL

    I just did the numbers according to dans caclualations and I came up with 1.40 oil and 1.30 electric for my costs right now. Thats a no brainer in my book. Oil prices are getting out of control.
    I will believe that the government is broke when the welfare checks start bouncing!!

  9. #9
    Join Date
    Sep 2004
    Posts
    654
    Double check your electric rate you pay....electric bills are loaded with added costs. My electric bill has one cost for generation charge, one for distribution, and then at least 5 other tidbit costs to add up to 18.6 cents per kwHr.

    Take your last months bill and divide cost by the total kwhr used, that is the true rate you're paying.

    And btw, electric tanks will rot out lonnngggg before the oil-powered tank is at half its life. Electric tanks need element changes whereas as indirect tank does not. Hmmmph, oil is cheaper, as always.

  10. #10
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    Quote Originally Posted by jeremy-lvhm View Post
    high efficiency? how is it efficient to burn oil at 3.50 a gallon on an 80 percent boiler??? I'm sorry but my electric is only .10 per kw hour and I'll be joining the ranks of putting an electric HWH back in my house and using it when oil is high and switching to oil IF it ever goes low again. I'm also putting in a high efficiency heat pump too. Don't tell me your like my neighbor and think indirect heaters are FREE because your heating the boiler for heat anyway. LOL

    I just did the numbers according to dans calculations and I came up with 1.40 oil and 1.30 electric for my costs right now. Thats a no brainer in my book. Oil prices are getting out of control.
    If you use those prices and 80% oil efficiency, you'd actually save about $2 after you've used 1,000,000 btus.

    140,000 btus x 80% = 112,000 btus divided into 1,000,000 btus = 8.93 x $3.50 = $31.255
    3,412 btus x 100% = 3,412 btus divided into 1,000,000 btus = 293.08 x $0.10 = $29.308

    Lots of people pay less for oil, and more for electric. Around us today, oil can be bought for about $3.27 a gallon. Boiler efficiency also varies, but 83% is more in line.

    Other intangible factors to consider are electric water heaters have greater standby loss, you still must keep a boiler on, so there would be less winter on/off cycles and higher seasonal efficiency, oil prices fluctuate, and can go down, electric rarely goes down, you can shop around for best oil price. These all must be considered.

    140,000 btus x 83% = 116,200 btus divided into 1,000,000 btus = 8.61 x $3.27 = $28.15
    Last edited by bobb25; 03-07-2008 at 06:17 AM.

  11. #11
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,233

    Smile Operating Cost Advantage = SIGNIFICANT

    Quote Originally Posted by im4snow2000 View Post
    Hope this is the right forum.

    Given oil's recent prices, he's considering switching just the domestic hot water to either electric or propane (he has propane at the property for a pool and cooktop in the kitchen).
    One should consider a heat pump for late spring to mid-fall
    pool heating in PA (perhaps ~ 7 + month swim season)

    C.O.P. > 4 at > 45'F ( 5.7 @ 80'F)

    http://www.aquathermheatpumps.com/titanium_at1200.htm
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  12. #12
    Join Date
    Dec 2002
    Posts
    317

    Talking "operating-costs"

    at todays oil prices all those
    "OIL-HEAT-TECHNICIANS" who "BAD-MOUTH" "LOW-MASS-BOILERS" are going to have to do some serious soul searching.. How about a
    "SYSTEM-2000" boiler for heat only delete the domestic heat exchanger its a cold start boiler anyway only runs on a call for heat up to temperature in 90 to 120 seconds and...... a "RINNAI" for domestic hot water

  13. #13
    Join Date
    Dec 2002
    Posts
    317

    Arrow Operating costs additional thoughts

    standard single pass boilers hold more water in the heat exchanger take much longer to reach internal temperature and are more labor intensive to clean.. even when oil was much less $$$$ it was always a wise choice for a low mass boiler example "CROWN-FREEPORT" as the # "1" choice for those wanting a "CAST-IRON-BOILER" a "BIASI" as the #"2" choice in Cast iron...... for serious $$$$$ savings a "EK-system-2000"
    "WHY" heat up a large volumn of water to circulate a small amount through a base-board system ?????

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