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  1. #1
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
    Posts
    1,018

    HVAC Energy Consumption Comparison Calculator?

    I often get ask about equipment efficiencies and cost to operate. Question I hear a lot are whether to buy a higher efficiency heat pump or furnace and how long is the payback or whether to use a furnace/AC or heat pump. With all of the different energy sources (Elect/NG), ratings (SEER,COP,HSPF,EER), different climates, and varying cost of utilities(tiered pricing,service charges,taxes,fees), tax credits, rebates, how do you come up with a straight answer? So the answer usually tends to be; it depends.
    Wouldn't it be nice if there were a calculator for this. Just plug in utility cost including service charges, taxes, and fees, your location, and equipment efficiencies and ratings, credits, rebates, and then voila, there's your answer.
    Anyone know of such a calculator?
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  2. #2
    Join Date
    Aug 2012
    Posts
    2,663
    I strongly believe a fireplace is the best heating option especially if you can supply your own wood.
    My name is TooCoolforschool and I am a chronic over charger.

  3. #3
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
    Posts
    1,018
    We have a gas furnace and wood stove in our home. We have to buy our wood but I think it's less expensive than natural gas with a 80% furnace and natural gas at $1.37/therm. The cost per therm includes service charge and fees. And you have to consider the cost of electricity for the furnace fan.
    80,000 BTU 80% furnace would use 80 cubic feet of gas per hour for 64,000 BTU of heat. That would equal 0.8 therm for a cost of $1.096 for 64,000 BTU of heat delivered. And that would equal $0.017/1000 BTU. And this figure does not include energy for the fan.
    A heat pump with a HSPF of 8 would deliver 8 BTUs/watt. That would equal 8000 BTU/kWh. At $0.10/kWh that would be $0.0125/1000 BTU.
    So it would seem that a heat pump with a HSPF of 8 (high efficient) would be 36% more efficient than a 80% gas furnace.
    But, is that true?
    I don't necessarily believe that a heat pump preformes that well in real world conditions. Some studies (http://www.fsec.ucf.edu/en/publicati...SEC-PF-413-04/)suggest that heat pumps actually perform at a rating of up to 50% less HSPF than nameplate in extremely cold climates. And up to 40% better HSPF in warm climates. For the area I live in I can expect a 20% decrease in HSPE. So That 8 HSPE would actually be a 6.4 HSPE. That would change the cost to $0.015/1000 BTU. That would make it only 9% more efficient. So I guess the answer; "it depends", is the best answer after all. PFM.
    Someone let me know if my math is close or am I way off track. Thanks.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

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