Heat Pump vs. Oil Boiler cost to operate

kerrygMay 21, 2008

I currently use a oil boiler (hydronic baseboard system)(tested at 77% efficient) to heat home and supply DHW. I have a separate Trane XL1200 central air system.

Considering replacing the 20 year old Trane AC with a heat pump and using it as primary heat with oil (hydronic) back up.

I currently consume approx. 1000 gallons of fuel oil each year for heat and DHW consuming approx. 139 million BTUs for both in the process. I estimate 20% of that is DHW alone leaving 111 million BTUs for heat only.

How much would it cost (at 13.5 cents/kwh in Maryland) to produce 111 million BTUs using a high efficiency 16 SEER Carrier Infinity heat pump?

I realize I will have to add the DHW back into the equation and I am considering an indirect-fired unit zoned off the oil boiler as an option.

Would like to incorporate Solar hot water into the hydronic and DHW eventually via heat exchangers but now just considering the change to a heat pump.

Thanks for the guidance....

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garyg

I live in Harford County in an all-electric home.

The cost of running a heat pump in the winter varies with the outside temperature. As outdoor temps drop, the btu's produced from the heat pump drops, and the C.O.P. (coefficient of performance) also drops. COP is the efficiency of the heat pump.

At 32F outside, a typical heat pump has a COP of 3.

Cost of 1 million btus at 13.5 cents per kw-hr, COP = 3:

(1,000,000 btu / 3413 btu per kw-hr) x \$.135 / 3 = \$13.18.

So the cost of 111 million btu = \$13.18 x 111 = \$1464.

Don't be fooled by SEER. 44% of the value of the SEER calc is at 67 and 72F outdoor temps. I don't run my a/c at these outdoor temps. EER determines your true cooling costs. Whichever SEER system you get, you want 12 EER and 9 HSPF minimum.

Also, because you are looking at a heat pump, you want full btus at the 47F rating temperature. Anotherwords, a 3-ton system should be 36,000 btu, not 33,000. Some condenser/coil combos are weak on heating btu's. The Trane XL16i is notorious for weak heating btu's.

Good luck.

May 21, 2008 at 8:59PM
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funnycide

there is no question that you should get a heat pump. The costs difference to go from an AC unit to a heat pump is minimal (maybe \$500 depending on...). You can set up your system to use the heat pump down to a certain outside temp (maybe 35Â°) and then use oil below that. The heat pump will be used in the mild weather when it is most efficient. The only catch is the air diffusers and grilles might not be installed for a heating system so some adjustment may be needed.
The cost for a million btu at 82% efficiency and \$3.60 gal for oil is \$31.81.

May 22, 2008 at 12:02PM
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