Woodstove and electric.

How long will it take to heat up? Forever, it would seem like.

If you want to trigger a warmup remotely (with an internet accessible thermostat(s) ) in advance of arriving, and want to avoid the cost of operating electric resistance backup strips, I don't think anything other than an oil or propane furnace as a secondary heat source to a heat pump would be suitable for you.

Ask a few HVAC contractors in the area for their advice. Heat pumps (whether ground or air source) are excellent at maintaining temperatures but setback recoveries, especially from a 20 degree setback, are probably a challenge that would take many days if even possible at all. I have a friend with a ground source heat pump system at a home in a moderately cold winter area that he visits 4 times a year for a month at a time and he only turns the thermostat down a few degrees, maybe 5, when he leaves. Because of the many hours it takes to recover from a setback, he doesn't want to deal with it. He's said he makes a bigger adjustment when gone during the summer in turning up the temperature setting, apparently the AC mode works faster than heat does.

Our camp (1300 sqft) takes about 1 1/2 to 2 hours to warm up the camp from 57 to 71 in very cold weather. We have propane. Zone 5. We have a thermostat waiting to be installed so we can control it from our phone.
Geo is very expensive to install. If you decide to go with propane buy your own tank instead of renting. That way you can shop around for the best fuel price.

Obviously, the recovery time depends on many variables.

I use heatpumps at a vacation home that we go to sometimes in winter. Before internet based thermostats, it was a challenge. I still find myself underestimating the time it takes but this was my first winter with the stats.

I have to say, it is really remarkable how the house doesn't heat up for hours and hours.

But keep this in mind, things are sized for the coldest temp. When it is really cold, you probably won't go. With that in mind, I think 24 hours on a relatively warm day to recover would be sized right. And of course on a really cold night, recovery would be infinite. Either way, heat strips, if needed, will usually pencil out better than keeping the house warm the whole time.

Much more important to build tight, well insulated structure. South facing windows help a lot. And don't forget straight air source heat pumps as an option. Rarely does geothermal pencil out financially and in a part-time structure, I don't know how it could. If you are going to have a propane anyway, do a good fireplace that can help recovery when needed.

We have geothermal at our house. I don't think I'd pay for it in a second home.

Admittedly I'm a bit shocked by some of the recovery times I'm seeing here. The only time we turn our thermostat down is if we're going to be away for several days. If it's winter, we turn it down to 55. When we return it typically takes about 3-4 hours to reach 70, but definitely not 24.

We've never upgraded to a wifi enabled thermostat. It doesn't make sense because we'd only use it a few times a year.

If I turn thermostat up 6 degrees in our geothermal house, it takes a couple of hours to recover (auxiliary strip heater turned off). If the 10Kw strip heat is turned on, it's much quicker.

Would you use the cooling very much? It's nice not to hear an outside unit when you're trying to get some peace and quiet in the country.

rrah, I am also surprised at some of the recovery times. We go to camp during the week and are at home on weekends. Camp (1300 sqft) is propane and home ( 2500 sqft) is heat pump with backup. The back up is definitely used in winter. Both places only take a couple hours to heat up from the 50s. I do love the wifi thermostat at home. It is nice to walk into a warm home.

If you winterize your second home and it is at 10 degrees I could see it taking longer, but not 24 hours. It does depend on the size, heat source, foundation and insulation though.

Most of upstate New York has design temperatures temperatures of about 0 F degrees for the winter, and about 85 F degrees in the summer. Given this is a new build and unoccupied for days at a time, it is doubtful you will ever see a return on investment on a geothermal system. Even with the 22% tax credit a geothermal system will be very expensive. Get some ball park estimates if you are curious. If your goal is to minimize heating and cooling costs, then invest the money in more insulation and better windows.

Are you going to install a gas stove and use propane? If so then a inverter type heat pump with a propane back up would be a good option. The inverter heat pump will perform well when the temperature is in the single digits. The propane back up could be programmed to do the bulk of the recovery during a set back. If you don't plan to use any gas appliances, then electric heat strips would be the back up. You could increase the size of the heat strips and have them staged so all heat strips used only during a large recovery period. Whatever you do you need to find a good HVAC contractor who knows how to properly install the HVAC system you want.

Why do you think you might want geothermal, energy efficiency, comfort, carbon footprint?

How many square feet will your home be?

How much land will you have, are you near water?

Will you be drilling a water well?

How long are you planning to own this home for?

How much will you pay for electricity, propane?

What type of distribution system are you planning for, forced air or hydronic?

Will you need air-conditioning?

How much hot water will you need?

What sort of budget are you planning for HVAC?

Will you need a backup source of energy?

SR

Where were you March 24th?