I may need to think about this more. Our current house has gas heat and a gas water heater. It looks like our peak electric use is about 66kWh/day. That is AC months - July/August. I'm guessing this would be useage in the cold months in the new house. The current house is smaller but was built in the 30s and insulation leaves much to be desired. Aside from a complicated system that the wife can't figure out I don't want half of the cost of my house going toward solar. I will see about contacting a Sol-Ark guy. It seems that might be the best bet.
This is a long post, but here goes. Open to comments/critiques from everyone, and I hope it gives you some food for thought. I'm in a similar situation as you - building a new home in a cold climate (Maine) with a desire for it to be all-electric and powered as much as possible with solar. Those last two things (all electric and solar) are proving to be a real challenge, due to winter heating concerns. So, I'm moving away from the ALL-electric stance, and shifting toward "mostly" electric (winter heat being the exception, because that's what would force me to dramatically oversize my system).
Here's where I'm at, although this might change:
1) Insulate the heck out of the building. R20 slab, R40 walls (double stud with dense pack cellulose), R60 ceiling. Triple pane windows, and not too many of them. Focus on barriers to water, air, vapor, thermal transfer - in that order.
2) Design for and Install radiant hydronic heat (in-slab for ground floor, low temp radiators for 2nd floor) with a good-sized buffer tank. Heat this with a propane boiler, and see where we are after the first winter. If heating requirements are as low as I hope, this will become only the coldest-weather heating system because we'll also use:
3) Air-air heat pumps (mini-splits). These will provide cooling and dehumidification during summer, when we'll produce more solar energy than we can use. They'll also provide shoulder season heating, which is sometimes needed for just an hour or two in the morning. Hydronic heating, especially via a slab, is not great for this situation as it tends to overheat. I can fire up the slab in November and run it through March, then shift to the mini-splits.
4) Install and use an ERV, simply because the house will be so tight. One of my favorite phrases is, "Humans, not houses, need to breathe. Houses just need to dry." See comment on barriers in #1 above.
5) Size inverter(s) to handle the mini-splits, induction cooktop, electric oven, heat pump dryer (my wife doesn't want a propane dryer), etc., but size batteries just enough to provide about 1-1.5 days of backup for everything, including the mini-splits. See more below re that.
6) I still haven't decided whether to connect to the grid, or if we do, whether to net meter / export to the grid. I'm hoping to avoid it. We pay about $0.28/kwh here because our idiot utilities are so dependent on natural gas, and our idiot legislature in the past tied the price of solar incentives for commercial farms to the price of natural gas, so when one price is high, so is the other. They're fixing that now as best they can, but it means we'll be paying high prices for electricity well into the future. Connecting to the grid seems to mean we're also more limited on equipment suppliers. The only reason I'm still considering it is the convenience factor for my wife if I kick the bucket or become so old and feeble I can't manage the system.
7) Back to the battery / days of reserve thing... Batteries are easily the most expensive part of a solar power system, so if possible, that's the place with the most opportunity to economize. It's also relatively easy to add additional battery storage in the future if the inverter-charger has been appropriately sized with that in mind. If we size them to provide 1-1.5 days WHILE USING THE MINI-SPLITS, that gives us several days of power in winter, when solar production is worst and we're heating with propane. For cloudy, humid days we can just fire up the generator during daylight hours and recharge if we stay off grid.
8) Use ground mounts for solar. Much easier to clear snow, far fewer requirements for rapid shutdown, and much easier repair and maintenance. Once my wife said she didn't mind seeing them, it was an easy decision. Only problem is trenching as we have much ledge (bedrock) near surface, but that's manageable.
To be frank, I think my desire to avoid fossil fuels initially led me to design a system that wasn't very practical for our climate. Our 3-3.5 hours of winter sun make solar heating really, really tough. Our energy conservation efforts (all the insulation, etc.) will minimize our fossil fuel use, but allowing it into the mix likely makes it much easier to stay off grid, and if we do connect, keeps the size of our array and battery bank much more manageable. Anyway, that's my thinking. Hope it's of some value.
