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  1. #1
    im in the northern va area.

    propane costs me 2.40 a gallon

    electric is .08 per KWH

    how do i figure out which is the best configuration for heat? all elec or elec/propane backup or straight propane furnace.



  2. #2
    Join Date
    Jul 2004
    Posts
    253
    I did the calculations on my new house with essentially the same costs for propane and electricity. Go with a heatpump with electric resistance strips in the airhandler as the backup/assist. Electric water heater also.


    Originally posted by miandsh2000
    im in the northern va area.

    propane costs me 2.40 a gallon

    electric is .08 per KWH

    how do i figure out which is the best configuration for heat? all elec or elec/propane backup or straight propane furnace.



  3. #3
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,148
    Punch the numbers in.

    For a high eff heat pump, use a COP of 2.5...

    Of course, aux heat with a heat pump will be more but defintely less than propane heat........

    Rarely do the numbers lie.


    http://www.warmair.com/html/fuel_cost_comparisons.htm

  4. #4
    thx.

    came out as:

    propane - 3.28 per 100K BTU
    elec baseboard- 2.11 per 100K BTU
    HP - .94 per 100K BTU

    is the elec baseboard equivilant to the heat strip (backup)?

    and what is the COP anyways?

    elec baseboard equals HP when i make this figure 1.1

  5. #5
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,148
    miandsh2000

    COP is an energy efficiency calculation. I believe it stands for Coefficient of Performance. As a rule of thumb, you can get a close approximation of COP by dividing the rated HSPF for your heat pump system by 3.4.

    Yes, electric baseboard and strip heat should be close to the same cost. Keep in mind that you only add the amount of strip heat required to supplement your heat pump based on your heating load calculation.

    Your situation for a new system seems like a no brainer.

    Good LucK!

  6. #6
    yes it does seem like a no brainer after seeing the numbers. thanks for the link. it helps make things a little clearer.

    is there essentially some sensor outside with a set point that tells the heat pump when to kick into emergency heat strip mode? and it this set point controlled by the thermastat inside?

    i found out that the trane 13i has a COP of 2.45 at 17 degrees and a COP of 1.98 at 2 degrees. not really sure what it really means yet but im sure i will need it sometime.

  7. #7
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,148
    miandsh2000

    I believe most straight heat pump systems use a thermostat to control when aux heat is required. When your HP in normal operation is unable to maintain your stat setpoint due to cold weather, then your stat would engage aux heat strips to kick in to supplement your heat from the heat pump. Depending on the amount of aux heat required, you can stage your aux heat. For example if you require 10KW of heat strips based on your heating load, dealer can install two 5KW heat strip modules. The stat would attempt to see if one module would satisfy your stat before kicking in the 2nd module on those real cold days. By no means am I an expert in this area but if you elect to go with a straight HP system, I would ask dealer about staging aux heat strips. Of course there is no strip heat with a backup furnace.

    Good LucK!

  8. #8
    Join Date
    Nov 2005
    Location
    Northern VA
    Posts
    512
    Sounds like you've already found this, but just to confirm.. I'n in the northern VA area too, did those calculations, and if you're on propane heat pump + strips is a no-brainer. If you have natural gas in this area, dual fuel is still the best way to go, but that could possibly change depending on what happens to electric and gas rates over the next few years.

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