Hello from BC, Canada

What type of system, PV or solar thermal ? If PV, I'd assume off grid capability ?

If solar thermal, for the reliability and complexity involved, while I'm a fan of solar thermal, you'll probably be better off practically and financially to keep burning wood.

I think we should start with PV and given the intent is to be a Grid Down system, I think it'd be an Off Grid system or similar.

Wood is available at no cost other than some fuel, chainsaw maintenance, time and effort and I have a lot of experience with hydronic heating so Solar Thermal is on my list of interests.

On solar thermal and hydronic heating systems: They can interface well, but I'd suggest getting more familiar with solar thermal for residential space heating applications.

One of the biggest considerations/drawbacks: For solar thermal, as the temp. diff. between the outside amb. temp. and the collector temps. increases (the collectors get hotter), the solar thermal system's efficiency drops, somewhat linearly.

And, most hydronic space heating systems operate and require temps. that are relatively higher than where most solar thermal systems are efficient enough to be economically viable. That is, where a solar thermal system's efficiency is relatively low.

Some comments FWTW/examples only:

A hydronic heating system might have an operating temp. of, say, 65 - 75 deg. C.
A very well designed flat plate solar thermal system under very good irradiance conditions at that operating temp. and so at a temp. diff of (70-(-10)C) = 80 C. with the outside environment might operate with a thermal efficiency of the panels of ~ 30 - 40 % less any piping/storage losses - if it's very well designed. As a practical matter, expect thermal efficiencies of ~ 20-30 % and more piping storage losses than you'll calc. Other practical considerations are freeze protection, probably via indirect systems that use glycol/H2O as the working fluid with heat exchangers and other ancillary equipment.

Evacuated tube collectors can operate at a higher thermal efficiency than flat plate collectors but do so with a penalty the evac. tube peddlers downplay or may not even know about: Their optical efficiency is generally less than that of flat plate collectors. The increased thermal efficiency is usually a bit more than the decrease in optical efficiency, but evac. tube collectors cost a fair amount more than flat plates and their operational track record is not as good as a flat plate. Also, depending on design, glycol/H2O may not be suitable as a working fluid due to the very high stagnation temps. an evac. tube system can achieve - higher even than the elevated and pressurized boiling points of glycol/H2O mixtures. Some jurisdictions, particularly the provinces, often disallow a lot of heat transfer fluids for environmental reasons.

Then, there's the likely question of thermal storage, sizing and maintenance. See the text reference below.

Depending on the application, your goals and the economics, you might be surprised at the size of the solar thermal system required to meet a part of the space heating load much less all of it. Depending on your climate, it may be more substantial than you think.

Bottom line here: If you have wood, and economics are a consideration, it'll probably be more cost efficient and probably require a bit less maintenance than will solar thermal.

If solar thermal is on your list of interests: A good tech. reference and what's probably the best, but by no means the only bible for solar thermal: "Solar Engineering of Thermal Processes", Duffie & Beckman. Reading/studying up is a lot more cost effective before a project usually results in a better outcome than simply throwing hardware at an application.

Less tech, but maybe good as an idea source: www.builditsolar.com. Just be careful and don't take that site too seriously. Lots of ideas, more than a few of which aren't well thought out, but for the most part more wasteful than dangerous.

Here's a well written article about solar heating in snowy north

That article demonstrates what is possible, but do note that clear blue sky in the background.
Mostly cloudy skies will change everything. Bruce Roe

A solar thermal system will not help us get through a 'grid down' scenario so we know that we want a Solar PV system so that is where we will start.

Thanks for that Link Mike90250. I followed it and found the University of Oregon site where I was able to plot a sun chart for my location:
05815903 Sun Chart Plot.jpg

I appreciate that.
I was responding to your comment about " ... a few Solar Thermal panels might also be helpful to keep the system warm and reduce cord wood consumption.", as well as your comment "Solar Thermal is on my list of interests."
Forget I brought it up.

Thanks JPM,
I appreciate your insight. We don't have any hand's on experience with either PV or Thermal so we're clearly on the steep part of the learning curve here.