calculate cost to heat or cool house
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  1. #1
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    Jan 2007
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    Westchester Co, NY
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    calculate cost to heat or cool house

    Hi all

    I have a simple question (Or maybe not). How can i determine the cost to heat or cool my house. I assume I need many numbers. So i guess I am asking 2 things really

    what specific numbers i need to calculate and then how to calculate
    HEating will be a duel fuel, hp + boiler

    I assume i need

    Heating BTU's
    cooling btu's
    Cost of Electricity
    cost of propane
    efficiency of Heatpump
    efficiency of boiler
    output of heatpump/boiler??

    what else?

    Thanks

  2. #2
    Join Date
    Jan 2004
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    Lancaster PA
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    BTU loss and gain of house.
    Ratings of equipment selected.
    HP balance point.
    Bin data for your area.
    Rates of electric and LP.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Jan 2007
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    Westchester Co, NY
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    Let me rephrase this i think - or ask a variation that may make more sense.

    I have seen the posts and responses where the knowledgable folks on here have shown that with a heatpump - it costs significantly less to heat 1 mm btu of heat Vs using propane or oil etc...

    What i am trying to figure out how long the payback is in going with the hybrid system Vs a the regular boiler. I finally have settled on a contractor to do a hybrid HP/Gas furnace system and a contractor that can do a hydronic gas fired boiler system. There is a 25 % difference in cost ( taking into account using the boiler for indirect hot water With the boiler system Vs installing a Gas fired hot water tank with hybrid system). Hybrid is the more expensive system

    So how long will it take to get payback of that 25% going with the hybrid

    Am I making sense?

    thanks

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
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    so ask the contractor for the hybrid sys to justify his premium--
    -- what does he think the time frame will be --
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #5
    Join Date
    Jun 2003
    Location
    Florida
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    9,548
    Quote Originally Posted by doogan123 View Post
    Let me rephrase this i think - or ask a variation that may make more sense.

    I have seen the posts and responses where the knowledgable folks on here have shown that with a heatpump - it costs significantly less to heat 1 mm btu of heat Vs using propane or oil etc...

    What i am trying to figure out how long the payback is in going with the hybrid system Vs a the regular boiler. I finally have settled on a contractor to do a hybrid HP/Gas furnace system and a contractor that can do a hydronic gas fired boiler system. There is a 25 % difference in cost ( taking into account using the boiler for indirect hot water With the boiler system Vs installing a Gas fired hot water tank with hybrid system). Hybrid is the more expensive system

    So how long will it take to get payback of that 25% going with the hybrid

    Am I making sense?

    thanks

    You have to have all your costs in order to calculate anything. In some areas,a heatpump might not be a wise choice if your electricity is high and your weather is cold...a heatpump loses it's capacity the colder it gets. When the heatpump's output goes below the balance point of your house(the temp at which the heatpump needs help to heat your home), you will have to run another heat source besides the heatpump. The best way for you to find out pay-back is to ask your local contractor(s).....ask them both what the payback will be.
    If everything was always done "by the book"....the book would never change.

  6. #6
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
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    769
    You will have central cooling with the heat pump system, and you won't with the hydronic heating system.

    That alone might be worth the 25% upcharge.

    Although I will say, all else being equal, hydronic heat is "nicer" than forced air, in terms of comfort and quite. But cetral cooling sure is nicer than window bangers.

    As far as the payback calc - beenthere stated the info you need. In a general sence (most areas), heat pumps are usually cheaper to run than propane or oil, and natural gas is generally the cheapest of any fuel. But, as I'm sure you've gathered, this varies by locality, and this variation effects the payback.

  7. #7
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    Jan 2007
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    Westchester Co, NY
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    Quote Originally Posted by beenthere View Post
    BTU loss and gain of house.
    Ratings of equipment selected.
    HP balance point.
    Bin data for your area.
    Rates of electric and LP.
    I am on the final stretch on selecting a HVAC system. As mentioned i have 2 systems competing at this time. On is 25% more than the other. The premium system is a bryant evolution hybrid. I think its a fantastic system. (15 Seer, 11.7 EER The second is a straight hydro Air with AC. Boiler would be a Buderus Propane GB142/30. 94% AFUE

    My last hurdle is to determine ( or closely estimate) the operating cost of each and the difference. I am trying to determine how long the payback will take on the premium system vs the Hydro.

    Beenthere - To respond to your items ( and hopefully you can help again ) I have compiled the below. I am unable to get everything but i hope its sufficient

    Electric Rate - 11 cents/KWH ( Fixed for 2009)
    Propane - 2.80
    Oil - 3.05
    HP Balance point - 32 Deg
    Bin Data - not sure what this is - however i got the average Heating degree days - 4804 and cooling degree day - 1190 for my area. Let me know if i need to get something different
    Ratings of equipment. I have not identified this. Cannot locate. I have a call into my contractor - however if this helps - the bryant furnace (2) are model # 355BAV042060
    The bryant HP (2) are model # 286AWA036000. 15 Seer, 11.5 EER

    For the second system - the heating is a buderus GB 142 / 30. First company Air handlers 24MBXB-HW (2)

    So - I would love to be able to understand how to calculate the operating costs. What else am i missing to do this?

    I have this asked of both contractors - however I need to be able to independently understand how to get this to move forward comfortably.

    Thanks guys

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Heating Degree days doesn't give you enough info.
    Unless you have the fuel consumption records for the previous year.

    Bin Data, is how many hours a year at what temps.
    EG: 641 hours between 65 and 60, 581 hours betweent 60 and 55, 780 hours between 55 and 50, etc.
    Then with the load clac, you can determine how much heat you need total for the hours at each of those temp bins, and determine seasonal cost from there.

    With your current rates.
    If you need 60,000,000 BTUs for the heating season.
    At the rates you posted.

    HP at an averaged COP of 2.5 providing 70%, elec Aux providing 30% = $1,121.59
    HP at an averaged COP of 2.7 providing 55%, 94% LP providing 45% = $1,268.11(LP hot air furnace)
    HP at an averaged COP of 2.5 providing 70%, 94% LP providing 30% = $1,124.25(LP boiler with hydro coil)
    HP at an averaged COP of 2.7 providing 55%, 82% Oil providing 45% = $1,111.25(Oil hot air furnace)
    HP at an averaged COP of 2.5 providing 70%, 82% Oil providing 30% = $1,019.68(Oil boiler with hydro coil)
    LP only at 94% = $1,942.65
    Oil only at 82% = $1,594.08

    Your house may need more or less heat.
    But, the difference in operating cost, will still be the same ratio as the above example.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
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    Jan 2007
    Location
    Westchester Co, NY
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    THanks - this is the comparison i was looking for.

    I just realised that I never posted my heat loss - Sorry it was very late....

    Heat loss is 64287 BTU
    Cooling load is 42280 BTU

    How did you get to 60 MM BTU - was this just an estimate?. Now that i have posted the heat loss - can this ce calculated?

    Thank

  10. #10
    Join Date
    Oct 2008
    Posts
    483
    OP, I don't think you need beenthere to recalculate this for you.

    If he guessed 60, and your heatloss is 64, that's pretty D&^% close. He already stated that it would be the same % ratio differences based on your heat loss, so just add about 7% to all those yearly costs, and there you go.

  11. #11
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    Jan 2007
    Location
    Westchester Co, NY
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    ok - so Beenthere used 60 Million BTU as what needed for the heating season to calculate. But the heatloss is 64 Thousand BTU (64,287).

    How should corrolate hese 2 numbers - I guess If I understood this i can figure out the rest?

    What i the heat loss calculation typically measured in - is it per day?, Per hour etc?

  12. #12
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    Quote Originally Posted by doogan123 View Post
    What i the heat loss calculation typically measured in - is it per day?, Per hour etc?
    BTU per hour.

    Take care.

  13. #13
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    Quote Originally Posted by beenthere View Post
    HP at an averaged COP of 2.5 providing 70%, elec Aux providing 30% = $1,121.59
    HP at an averaged COP of 2.7 providing 55%, 94% LP providing 45% = $1,268.11(LP hot air furnace)
    HP at an averaged COP of 2.5 providing 70%, 94% LP providing 30% = $1,124.25(LP boiler with hydro coil)
    HP at an averaged COP of 2.7 providing 55%, 82% Oil providing 45% = $1,111.25(Oil hot air furnace)
    HP at an averaged COP of 2.5 providing 70%, 82% Oil providing 30% = $1,019.68(Oil boiler with hydro coil)
    The 2.7 and 2.5 COP seem a little low. This was based on the Bryant model provided and the bin temps?

    He stated his balance point was 32F.

    My Goodman 3 ton has a COP of 3.25 at 35F.

    Thanx and take care.

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