Our neighbors use a geothermal heatpump and they also have a gas furnace. They are older people (80+) and keep in really warm in there. I was in their house last Feb. and I was sweating with a T-shirt. lol
Do they keep it at 60 F in the summer?
I've seen this a few times and scratch my head over why folks will try to grow icecicles indoors in summer, and scorch the wallpaper in winter. I run about 80 in summer, 69 set point in winter (corresponsing to 66-67 F through most of the home...except the central hall above the main ductwork where the thermostat is located.)
What I don't like about heat pumps is the low air temperature they put out. It would be easy to install one as I already have central AC.
That's a concern I've had as well. I would want gas back up. Electrical strip heaters are thermodynamically inefficient for fossil fuels. Electrical generation efficiency here is tied to the old coal plant nearby...less than 35% thermal efficiency for the delivered juice. An 80% efficiency furnace clobbers a strip heater in that regard.
The other factor for me is that where I grew up we had blizzards every 5 years or so that would knock out electric from a few days to a week. We had a nice 1930's (?) era Autocrat wood cookrange/oven and a large fireplace, plus a single large propane heater, so it really didn't hurt us other than being stuck with kerosene lamps and candles and needing to move some refrigerator items to a cooler on the back porch. I've since experienced this sort of long electrical outage even in ice storms in the city down in Texas. With a generator it should be possible to run the furnace at least periodically in a northern climate. I plan to install a panel in the next year or two so that I can run the furnace and a few other circuits this way as needed.
To give you an idea, the peak that the two of us have used is about 4400 kwh in one month. LOL That is not heating upstairs for the most part, turning off heat at night and when away, and keeping the main floor at like 67F. We have since added a layer of R30 to the attic and the peak since that time has been more like 3300 kwh. House is a bit over 3000sq.ft, 40 years old, single pane glass.
Ouch, that's over half my annual electrical use. If you normally use 1,000 kwh in a non-heating/non-cooling month then that would be perhaps 7 HSPF or 3400 kwh * 7 = 23.8 million Btu. With an 80% gas furnace this would be 23,800,000/0.8/100,000 Btu/ccf ~ 300 ccf natural gas per month! That assumes I've done the calcs correctly...but I've never had a heat pump so I might be way off.
Gas or electric for the water heater? I assume electric since you mention not having any gas payment unless you install a gas furnace.
Lynchburg's average daily temps are about 7 F higher than ours from Dec-Feb. We are heating about 2800 sq. feet...and unfortunately, due to missing insulation between the spaces, a three car garage as well...though not intentionally...and not permanently. Our gas use should peak under 200 ccf/month this year, down from about 230 last year barring a much colder month this year. The 7 F difference is worth about 30 ccf/month, perhaps more, based on my empirical furnace model.
I want to install a sealed combustion high efficiency two stage furnace to knock about 15% more off. And I need to insulate the ceiling of the large garage cutting another 7-15%. I've already remedied several uninsulated spaces, greatly improving the comfort of several rooms, plus saving energy. Sealed combustion will allow me to complete my sealing of various air infiltration penetrations into the utility space and reduce other infiltration routes as well.
Only thing that I don't like about gas is paying for having the service during all the months where I am not using any gas. Not a big deal, but something to consider.
Yes, this is a considerable cost adder when going from no gas, to some gas. I had this same problem down in southern Georgia. We had about 0.08/kwh electric, an electric water heater, and high efficiency outdoor gas furnace. Why it still had an electric water heater I do now know, I was just renting temporarily. The electric water heater plus monthly gas hook up charge was the worst of both worlds during cooling season.
If I was to set up a home today from scratch I would go with gas water heating (storage...perhaps condensing), gas furnace (condensing, sealed combustion), and a gas clothes dryer. I would probably also set up an 8 month/year passive solar water heater loop. I suppose if money was no object I would use a ground source heat pump, passive solar water heat, and PV solar instead of the above. It's debatable whether it would make sense to then use gas for water heating and the dryer. My wife would like a gas range too...and I would like one for some wok recipes and Indian food--wouldn't have to use the big burner and lilttle propane cylinder outside anymore.