Heat Pump vs Central Air Unit

[genmaster]

Hi All,
I am preparing to replace my 25 yr old oil fired forced hot air furnace and central air coil and condenser. With higher oil prices these days, I'm considering installing a heat pump instead of the condensing unit. I live in the northeast US and am wondering if it will pay to go with the heat pump so that I'm not actually on oil until it gets down into the low 30's. Any thoughts or experience would be greatly appreciated. Thanks

 

[Dana]

Since you have a heating history on the place you may be able to use the old boiler to measure the design heat load.

Alternatively, run a Manual-J or IBR type heat load. If you're super-aggressive about air tightness and R-value assumptions you can still get reasonable numbers out of free online, or cheap load calculators. But keep in mind the garbage-in = garbage-out rules. Most newbies tend to err WAY to the conservative side, which ends up sub-optimally oversizing the equipment.

There are quite a few cold-climate heat pumps that work down to sub-zero temps with specified output even at temps cooler than -10F. When you know your design load and design temperature you can search NEEP's database to narrow down the options.

The better cool climate heat pumps utilize vapor-injection scroll compressors to extend both capacity and efficiency to much lower temperatures than the old-school heat pumps you may be thinking of- there's no need to switch over to oil if sized correctly. Some have options to add auxiliary resistance heat to the output when the compressor isn't keeping up, but if done reasonably even when the heat strip is running the heat pump is still delivering the lion's share of the heat. I could heat my whole 2400' house (+1600' of basement) at 0F outdoors with some 3-3.5 ton cold climate heat pumps without needing to add any strip heat.