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Community and Q&A

Propane fired vs Heat pump HWH

k8RQsvj3yc | Posted in Energy Efficiency and Durability on

Has anyone seen any direct comparisons/reviews of using propane fired HWH (tank & tankless) vs a heat pump based HWH?

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  1. GBA Editor
    Martin Holladay | | #1

    In most areas of the country, propane is a really expensive fuel. My latest delivery cost me $3.32 a gallon -- and I only got that price because I locked it in early in the season by committing to a pre-pay program. Other customers in my area are paying $3.80 a gallon.

    And remember -- propane supplies only 66% of the energy per gallon of fuel oil. It's a weak, dilute fuel.

  2. k8RQsvj3yc | | #2

    My home will be very rural. My main use of propane will be to fuel the standby generator. Main Heating will be heat pump (air source or geo), I will have a propane furnace as a backup to automatically cut in when/if too cold for the heat pump (central PA zone 5).

    I'm undecided on HWH and was looking for info to help. From an operating standpoint what is the cost of an electric heat pump HWH vs the propane. Last I checked (if you own the tank), the propane cost was 3/gallon, If you lease it was much higher. I haven't checked in a while.

  3. GBA Editor
    Martin Holladay | | #3

    The answer depends upon your local electric rate.

  4. k8RQsvj3yc | | #4

    Current rate is about 9.1 cents pe kWhr

  5. wjrobinson | | #5

    Jim, my electric is 16 cents/KW and rising. Propane is expensive similar to Martin. Wood pellets and NG are 1/4 the cost for me. GSHP is tough for me as contractors are charging big bucks here.

    Passive solar and NG and pellets here win the prize.

  6. wjrobinson | | #6

    PA seems like the wrong location for a HPHW Heater. With all that you are spending install solar hot water and a super heater and or a condensing tankless propane unit.

  7. GBA Editor
    Martin Holladay | | #7

    Here is the math:

    $100 of propane gives you about 30.1 gallons, or 2,759,036 Btu. Most propane water heaters have an efficiency of about 62%, so you end up with about 1,710,602 Btu.

    $100 of electricity buys you 1,098.9 kwh of electricity, equivalent to 3,750,549 Btu.. If your HPWH has an average COP (including the occasional use of the electric resistance coil) of 2.0, then 1,098.9 kwh of electricity will give you 7,501,098 Btu.

    So, using electricity to heat your water (with a heat-pump water heater) gives you 4.4 times the amount of hot water as propane would for the same $100 of fuel.

  8. k8RQsvj3yc | | #8

    Martin , that is the breakdown I needed.

  9. wjrobinson | | #9

    Kool aid math though may still favor electric since your rate is much lower than mine. Condensing +Navian 98% and the heat pump is stealing home heat and not getting COP 2 in my cellar.

    Martin, are you now thinking the heat pump water heaters make sense in a cold Climate like the Adirondacks?

  10. GBA Editor
    Martin Holladay | | #10

    Whether or not to choose a heat-pump water heater depends on many factors, including:
    1. Whether you have access to natural gas
    2. The local price for natural gas or propane
    3. The local price for electricity
    4. Your climate
    5. Whether you have an appropriate location for the water heater
    6. Whether the cooling side-effects are desirable or undesirable
    7. Whether cooling the room where the water heater is located will cause problems (for example, very low temperatures that prevent the heat pump from operating)

  11. wjrobinson | | #11

    Also recovery rate, replacement cost, noise are considerations.

    Installed near a boiler or pellet stove or woodstove that is nice and warm, I could just maybe try one out.... Or not.

    I feel my arm slowly being twisted as this subject comes up.

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