Questions re: cost comparison HE heat pumps vs. HE furnace - CENTRAL OREGON
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  1. #1

    Questions re: cost comparison HE heat pumps vs. HE furnace - CENTRAL OREGON

    Hi Everyone -

    I've recently purchased a home where the previous owner had only air handlers with strip heat installed. I can't imagine why.

    It's a big place (4700 sq. ft) in Bend, Oregon, which has a climate roughly similar to Pendleton, OR (I think). I ran heating comparisons on

    http://www.hvacopcost.com/

    using data I think is representing the latest/greatest - I tried to compare a 9 HSPF heat pump system to a 95% AFUE natural gas furnace, and the calculator indicates a savings of the furnace vs. the heat pump of $3874/yr. Could that be right?

    I've been talking with several HVAC contractors here, many whom have recommended heat pumps, but I can't get anyone to help me estimate the estimated yearly costs of HPs vs. furnaces. There seem to be a lot of folks excited about heat pumps - the DOE (energy.gov) and others.

    It's a very mild summer here, so the cooling of the heat pump doesn't excite me much. That's what ceiling fans are for.

    Complicating matters is that to install a furnace, we'd have to pay to extend the gas main up to the house - this could cost several thousands of dollars. However, my primary concern is the marginal costs, including utilities and expected maintenance.

    My questions are these -

    1. Do the comparison numbers seem accurate to the pros on the forum?
    2. Am I missing something about heat pumps - much of the info on the net, and my local HVAC guys seem to think they're great even in a climate like Bend... but we spend quite a bit of time at or below freezing (it's not like MN or MT, but still).

    Thanks in advance, all. Much obliged.

    Nathan

  2. #2
    Join Date
    Jan 2004
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    Lancaster PA
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    Post your electric and gas rate.

    With the savings rate you posted. Using electric strip heat only must be costing you around 15,000 bucks a year.
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  3. #3
    Join Date
    Feb 2009
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    Portland OR
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    Quote Originally Posted by beenthere View Post
    Post your electric and gas rate.

    With the savings rate you posted. Using electric strip heat only must be costing you around 15,000 bucks a year.
    No, you are doing the math backwards. If he is saving $3874 per year that means that his cost with gas would be around $1,500 and he was spending almost $5,000 with electric. Here in Portland(over the mountains about 120 miles from bend) gas is about 1/3rd the cost of electric. I would say savings of $3,874 could be very possible with a natural gas furnace. A Heat pump would be a nice addition for your home and bend is not usually a mild summer, I go rock climbing in Terrebonne(25 miles north) and it will be in the hundreds for days and in the 80s at nights. If natural gas is available that will probably be the most cost effective. If you only have propane or electric than either a geothermal or a heat pump will at least help.

    Also post up how much you are spending per year on electric for the house and your high bills in the summer vs your low in the winter so we can determine a baseline electric cost on the home.
    Let me know if there is anything I can help with since I am located in Portland.
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  4. #4
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    Whee do you see that he was spending only 5,000 with electric strip.

    he said a gas furnace would save him an estimated 3874 over a heat pump. So he would have to have a much higher heating bill then 5 grand with just strip heat. I think.
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  5. #5
    Join Date
    Feb 2009
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    Portland OR
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    Quote Originally Posted by beenthere View Post
    Whee do you see that he was spending only 5,000 with electric strip.

    he said a gas furnace would save him an estimated 3874 over a heat pump. So he would have to have a much higher heating bill then 5 grand with just strip heat. I think.
    Oops, I thought he was going to save $3,874 over electric strip heat and for a house of that size $5,000 a year in electric would be VERY easy to hit, Bend is a harsher climate than portland and houses in the 4,000 sq foot range are about that per year if all electric heating or propane.
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  6. #6
    Wow - I think I've stumbled upon one of the most helpful forums on the internet... thanks for the help, all!

    Strip heat for us right now is insane - our first bill was $1200 in a month, and we've been pretty careful. So we're going to make MAJOR improvements with EITHER gas or HPs, so there's no real WRONG answer here.

    I've re-run the calculations using the local electric rate of 11.5 cents/kwh, and I think the online tool's estimate of 107 cts/therm for gas is pretty close (not sure, as we're not currently Cascade Natural Gas customers, but will be if we install the furnaces). I think I had put a squirrely number in for BTU's above to get the crazy numbers I did. I found a BTU to TONS conversion - we've had HVAC contractors recommend 3 ton equipment upstairs, and 5 ton downstairs, so the 80,000 BTU number is pretty close too.

    Anyway, using THESE numbers, the estimated operating costs of 9 HSPF Heat Pumps is $3021, and the 95+% AFUE Furnace is $2663. I actually think the Heat Pump estimate might be a little low, as it's been really cold and using strip heat will catch up to that number really, really quickly. In any case, I thought I had understood that the operating costs of HP vs NGF were pretty close here - these numbers make more sense, and are numbers we can live with.

    Although I'd have to pay a contractor to dig a gas-main extension and a trench for a service line to the house, I'm leaning towards installing the furnaces now - I think the wife will like the gas heat better when its cold, and the cost for installation is lower (even with the trench), and if the estimator is right, gas has lower marginal cost for operation in our environment. Then, if finances and will allow, we could install a high efficiency HP downstairs sometime in the future to handle the fall and spring more efficiently, and the cooling during the summer will be nice.

    Questions
    1. Does my current math look about right?
    2. Is my thought process reasonable, or am I missing something that you pros can alert me to?
    3. Is the staging to the improvements the right path - furnaces first, then evaluate for possible future HP's?

    @SkyHeating - I really do appreciate your help. TerreBonne is MUCH hotter in the summer than is Bend - we're on the north slope of Awbry Butte, and we're more in the Cascade microclimate than the high desert. Climb Smith Rock in the spring and fall, and leave the high summers to the mountain bikes and rivers!

    Let me know if I'm stepping into a bear trap, otherwise I really appreciate everyone's help. You've got a great resource here - don't let any trolls or spammers screw it up. Many thanks!

  7. #7
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    Step 1 - install anythign other than strip heat.
    Step 2 - son't overthink step 1

    You have ductwork already installed? IF just electric baseboards, then look at a minisplit.

    Otherwise, I would take a look at geothermal. In some case it compares favorable to a dual fuel system after tax credits.

    With a home that large, I would also strongly consider zoning it.

  8. #8
    @ motoguy128 -

    1. Ductwork is already in. The upstairs air handler (and future furnace) is in the attic, which is unconditioned-space - we'll insulate that pretty much immediately. We have some heated floors in the house (bathrooms, a sunroom, and the breakfast nook), but haven't been using them for fear of the cost - they're on resistive heat too. Are the heated floors super expensive to run?

    2. I'm told that geothermal isn't an option here. The house is located on the north slope of an old volcanic cone - I don't know where the water table is, but I imagine it's deep, and not trivial (!) to bore down to through volcanic rosk. The property is too small, sloped, and too rocky to consider shallow loops.

    3. The house is already on zones, but the zones don't seem that effective - during the day, when the kids are awake, the majority of the house is heated by the downstairs heat zone. All the warm air rises up the staircases. At night, it kinda works to let the bottom floor cool and keep the upstairs warmer, but I haven't been too impressed with the difference.

    A question - should we go ahead and use the warm floors? We've pretty much had them turned off...

  9. #9
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    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

  10. #10
    Join Date
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    Electric rate is a bit too high which makes the heat pump operating cost
    higher than I would have initially anticipated.

    I don't know much about your 4,700 square foot house

    W.A.G. =
    6,000 ………… Heating Degree Days
    82,000 ………… BTU/Hr at 20'F
    240,000,000 ………… BTU Heat Loss per Year
    …………
    90.0% ………… Efficiency
    2,666.67 ………… Therm used
    $0.80 ………… $ /Therm ( previous post)
    $2,133.33 ………… NATURAL Gas Annual from CNGC
    …………
    3,413 ………… BTU per Hr/ kW
    70,319 ………… kW
    3.1 ………… COP
    22,683.67 ………… net KW for new Heat HIGH EFFICIENCY Pump
    $0.115 ………… $/ kW
    $2,608.62 ………… minimum Electric Annual for HSPF > ~10
    …………
    122% ………… Heat Pump/ Natural Gas

    BUDGET BUSTER
    $8,086.73 ………… Strip

    Very quick heat loss would be ~ 82,000 BTU/hr ( same as you have estimated)
    Last edited by dan sw fl; 01-10-2013 at 02:20 AM.
    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

  11. #11
    Join Date
    Nov 2004
    Location
    SW FL
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    http://www.climate-zone.com/climate/...gon/pendleton/

    Annual heating bill can vary by 25% just due to variation in Heating Degree Days ( HDD)
    for your locale and each year is a bit different than " a norm".

    i.e. range of HDDs might be ~4,800 to 6,200 in your region

    P.S.
    __ Was the previous owner the president of the electric utility?
    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

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