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Dogwoods666 · Sep 12, 2008, 01:19 PM

I live in southeast Pennsylvania. I am installing a new HVAC system and am wrestling with whether to go with a "standard" Oil Furnace and AC unit versus a hybrid which includes a standard oil furnace along with a 16 SEER 2 stage heat pump with AC Unit... which is an additional $1400 over the standard system cost.

The justification... less oil, seems real, with oil as a second alternative when the heat pump is not as effective... but then again, I do not really know much about this area of expertise.

Can anyone give me relevant data and/or experience to help me make this decision?

Thank you

EPMiller · Sep 12, 2008, 06:07 PM

I can only give you my opinion because there are many variables that come into the equation. I live in the same geographic area and it seems to me that heat pumps do a pretty good job around here if they are installed correctly (think unit sizing and proper ducting, definitely not a jumble of flex in the attic!)

Rule of thumb, when the outdoor temperature gets below something around 17F, heat pumps don't put out much heat for the energy required to run them. Depends on the design of the unit. We don't get a lot of weather like that around here, so they work pretty well most of the time. If your house is efficient (reasonable sized, well insulated, tight) and you don't want to heat it to 75F or above, heat pumps are efficient. I still like electric backup too even though the price of electric is going to jump seriously in the next couple years. If you need 20kW or less of heat, it is pretty cheap to install. If you get your installer to stage it so that it doesn't all come on at once you can save a bit there too. Dual fuel requires you to maintain that oil burner even if you don't use it much.

All that said, I like ground source heat pumps the best. They work very efficiently no matter how hot or cold it is outside. Did you look into that?

letmetellu · Sep 12, 2008, 07:34 PM

I live in the west and don't have much knowledge about your winters but here our winter nights average around 35 degrees. Most heat pumps are designed to cut out at around 35 - 40 degrees, that will automatically turn on the oil burners. So if your winters are colder than what I have you are going to be using the auxiliary heat very much.

EPMiller · Sep 13, 2008, 07:06 AM

Originally Posted by letmetellu

<snip> here our winter nights average around 35 degrees. Most heat pumps are designed to cut out at around 35 - 40 degrees <snip>

That's interesting. The heat pumps I work on do not have a cut out setting as such. The only way you can shut down the compressor is to manually set the tstat switch to emergency heat. On the better installed systems, that is rarely if ever necessary. On the systems with poorly insulated ducts in the attic I agree, they don't do well. But a fossil fuel furnace through those same ducts will have the same losses.

Our systems automatically call the backup heat, but the heat pump keeps on working. Even at 20F outdoor, they are contributing something. The costs for heating with a heat pump vs fossil fuel are competitive around here. But the maintenance costs for the added oil burner make me question it unless the house has very large heating needs.