crdnh

what is your electric rate?

have you even considered geothermal heat pump or ruled it out?

for furnaces
95+% AFUE efficiency
2 or 3 stage or full modulating with var speed blower
For your area/winter climate, I think it would be a mistake not to look at the full modulating mdls

for heat pump
15 SEER minimum, 12.5+ EER, 9+ HSPF

IMO

crdnh

one more thought

consider going all electric with conventional heat pump.

I would stay away from the Hallowell Arcadia.

see link on fuel comparison calculator.

IMO

Here is a link that might be useful: Fuel Comparison Calculator

I would suggest adding an electric plenum heater to your propane system as a backup in case you run out of propane during a cold snap.

The ideal system would be a geothermal split system with a Carrier Infinity propane furnace as the air handler & backup. You would not need the electric plenum heater in this case.

-18F is mighty cold! I would suggest putting more money up front into a better system (geothermal) than paying it out for energy that has no end and no return. Keep in mind that a geo system has the longest life cycle of any active heating/cooling system and will lower your DHW costs as well.

BTW: We live in Montreal Canada, mighty cold winters here too! Last year's heating (360-days) cost us $485CAN ($548CAN w/Tx), 7731kW. Neighbors seem to be paying ~$2k-$4k for heating comparable sized homes. Canadian & US dollar are very close to par at this time.

We heat with a 3-ton DX geothermal HP.

Geothermal is awesome.
If they don't have the extra-funds for geo-thermal get a 2.0 ton highest efficiency single stage heatpump. You would be better off staying on the high side of the correct size unit. So if they say between 1.5 and 2.0 go with 2.0.

Spend a little extra like the previous poster and add heatstrips in the plenum. The time to do it is now when everything is new and easier to add.

How big is the house? If max heat loss is 45K btu per hour and your main source of heat is heatpump you may want to consider upsizing to 2.5 tons if your ductwork will allow it. Do you have alot of days below 20 degrees? Upsizing would help you have a lower 'heatpump only' heat maintain temp.

Thanks to everyone. Energy costs in NH are high - about $0.15/delivered kwh and currently over $3/gallon for propane.

You don't see heat pumps as the primary heating system in our climate, as the average temps December-March are too low. But when they can operate efficiently, heat pumps are cheaper than propane (no NG available) even though our electric rates are high. The 2.0 ton heating capacity is about right -- if any more heat is required the outside temperature is likely below 30-35 degrees.

I did not investigate geothermal beyond seeing that the cost seems very high, especially the ground loop, compared to higher efficiency conventional systems. fsq4cw: the low annual costs are appealing, but what was the up-front investment?

So, it seems like:

- Single stage heat pump SEER=>15, HSPF=>9
- Heat strips in plenum
- Modulating, variable speed propane furnace
- AFUE for furnace => 95%

keep in mind you should be able to heat with your heatpump well below 30 degrees F. With a new, well-insulated house your properly sized heatpump should be able to maintain normal temperatures to atleast 20 degrees or even colder without running auxiliary. Even if you heatpump is running nonstop it won't break the bank. I would think that running the heatpump non-stop at 15 degrees fahrenheit with electrip strip backup engaging rarely is cheaper than propane.

crdnh

have you looked at the fuel comparison calculator? you should! using a COP of 2.75 for electric and 95% eff for propane, a high eff heat pump is less than 1/2 the operating cost of propane on a BTU basis. I would have to think long and hard before I went propane backup.

take a look. of course you would have to rely on heat strip backup. but you might consider oversizing the HP and going two stg condenser.

something to think about if operating costs are important to you and GEO has been ruled out.

IMO

tigerdunes - Geez, and there I was thinking I'd asked a simple question. I did do the comparison, but with lower COP numbers since average overnight low temps are: Dec=15f, Jan=7f, Feb=10f. Doesn't the COP drop below 1.5 at around 10f?

So the backup resistance heat (and I'd need like 15kw) would be carrying most of the load during the coldest part of the year - and that came across as more expensive than propane in the calculator.

I also wonder that you never see a heat pump as the primary system in my area, although I have heard of (but never seen) the Hallowell Acadia systems. I'd sort of viewed the heat pump as an efficient "free ride" during the shoulder season and on mild winter days.

And we'll have propane for cooking, so we don't get to eliminate the fuel entirely. But it's food for thought.

crdnh

consider a gas log fireplace system in for ambiance and supplemental/aux heat for comfort with a high eff HP system.

IMO

I know the COP of a heatpump thats about 15 seer with the matching air handler and coil is about 2.55 at 17 degrees. On goodmanmfg websites it has some detailed specs of the efficiency numbers of their heatpumps. The 15 seer single stage heatpump has a COP of 2.07 at +5 degree F.
Basically in cold temps your heatpump would run non stop and the aux would sometimes come on.

You might be surprised how infrequently your aux heat comes on if your heatpump is running correctly and your house is insulated well. Heatpumps are good at maintaining temp. Not so good at bring it up.

Propane for the fireplace is a good idea as an emergency heat source and nice ambiance.

The up front cost of our geo system was about $18k, A-Z - including re-landscaping; that was 7-years ago. It was maybe $8k -$10k more than a conventional system. However IâÂÂm sure we have already seen our payback. In retrospect I would certainly do it again - even at todayâÂÂs higher installation costs.

The major difference in cost between a conventional system and a geothermal system is the ground loop. Your 1st costs of any system will be always be the lowest. These costs can be further reduced in new construction by planning to have the borehole(s) drilled within the envelope of the foundation right where the mechanical room is planned - before the slab is poured. That way your project will not require digging & trenching, insulated runouts etc..

I canâÂÂt understand why air-source heat pumps are not common for your climate as itâÂÂs not any colder than ours. Air-source heat pumps are very common here and are set to cut out at ~10ðF. However, your electrical rates are indeed higher. Keep in mind that even with your electrical rate of ~15â/kW and a 4-COP, with a geothermal HP, the cost per kW of heat delivered into your house would be ~3.75â/kW.

Regarding the use of heat strips, remember that a 15kW heat strip can be staged so that not all 15kW come on at once, particularly if theyâÂÂre not all needed.

Be sure to have ductwork that is properly designed and installed for the cfm required. Now would be the time to consider zoning, if it may be required. If your house will be tight and requires an HRV be sure to calculate some additional heat loss because of the HRV. If you choose an air-source HP and want to âÂÂup-sizeâ then perhaps choose a 2-stage HP and definitely a variable speed air-handler or furnace.

Tigerdunes suggestion of a gas fireplace is an excellent suggestion since you plan to have propane anyway, but you still need a plan (plenum heater) in case you run out of propane.

SR