If it's very cold in the winter (e.g. below 0 F), you should use the wood furnace to help out the geothermal system. When the temps are that low the geothermal system can have challenges keeping up with the heating demand. You can use the wood furnance anytime you are a bit cold in the winter and want to get the cabin up to temp faster. But, be mindful with wood usage. Now that there is nobody living up there full-time, it's harder to get more wood stacked up in reserve.
If there is a strange smell when you first startup the wood furnace, it could be because it is too hot and is burning dust in the ventilation pipes. Go down to the furnace and place your hand on the silver top towards the back. If it is too hot to touch for more than a few seconds, the furnace is probably too hot. You will want to close both dampers on the front of the furnace to limit incoming fresh air. You will also want to be sure the vent into the man cave is wide open so it is dumping heat into man cave room.
Geothermal is the primary heating and cooling source during the day. It will heat in the winter and cool in the summer. There is a 500 foot deep well that pulls water from deep down and the unit uses the temperature differential to heat or cool depending on the need. Science is cool.
Be sure the geothermal breaker located on the geothermal unit is ON.
Arrowhead Electric, the local electric utility, has off-peak heat. During "off-peak" hours (10pm - 6am), the electricity price is 50% less than the normal "on-peak" hours. There are several Steffes off-peak thermal heating units throughout the cabin that take advantage of this by storing electricity as thermal heat in bricks throughout the night. The heat is then released throughout the day to minimize electricity usage for heating during on-peak hours. You can read more about it here.
Arrowhead Electric controls the off-peak usage to the cabin through the use of a control relay near the electric meter. At 6am, the relay opens and you cannot even use the Steffes off-peak units if you wanted.
This is set as AUX heat in the thermostat wiring and in the Nest thermostat.
The geothermal unit has an electric emergency backup heat option if something goes wrong with the main geothermal heat pump system. It can be activated manually through the Nest thermostat and probably on the unit itself. It should automatically turn on if the inside temp hits 45 F.
If there is a power outage in the winter, your only source of heat will be the wood furnace. Get that puppy going and hope it doesn't last too long. If the power goes out, no one is at the cabin, and the winter temps are very cold. You have to either hope the power comes back on soon or make an emergency call to a neighbor. Brad and Judy Sillman would be the best bet as they are next door and live nearby. Betsy could be a last ditch effort, but keep in mind she lives in Grand Marais. See Contacts
I would estimate the cabin will last up to 24 hours with no electricity before it gets to 32F inside, if outside temps are below 0F. Halve that if there is a lot of wind pulling heat off the cabin.