Solar in winter is a hit n miss deal.
The angle of the sun through the atmosphere, which becomes greater the farther from the equator one lives, and the shorter length of the day offset the cooling of the panels and wet cell batteries become less and less effective the colder they get. Physical and mppt tracking can gain some of those losses back, but add complications to the system. Storms are more frequent as are cloudy days. Snow covered panels don't charge batteries, at least mine don't. In late fall I've had leaves plastered to my panels after storms and had to peel all those off.
This brings up a question I've never seen addressed or even considered;
How much snow/ice load can industrially constructed PV's sustain without damage?
When it snows here it is often very heavy and wet. We got about 14" and it came quickly this past winter. My truck would barely move until I brushed off 1/2 ton of snow. Should we add that to the list of complaints about solar in winter?
All that being said I sure would hate to go into winter without the meager array we now have. (750 Watt). This is my third set of batteries since we moved here a little over 8 years ago. First set 4 6V golf carts, burned up in 18n months. Far too fast charging cycles followed by far too deep (read dead as a doornail) discharge cycles. Doubled that to 8 and made those last 3 years, still with very little solar and unregulated charging. We then spent some coin on our PV's and a good charge controller (C-40) and this 12 battery 6V to 12V bank just sets there at 13.4 90% of the daylight hours. These batteries hardly even use any water, and the plates are all gunmetal greyish with no sign of warping or thinnng. I credit this battery life entirely to the adding of the slow steady input from the PV's and the regulated self equalizing mode in the C-40. Yet I sometimes have to run the Kubota to make up for big loads/uses (sawing, drilling, ect.).
The bottom line is I wouldn't expect your panels to produce as well in the winter, overall, as they do day in and day out in the spring and fall. The heat issue with PV voltage drop, and heat in the batteries reverse the effects of winter with the same results. Wet batteries can be far easier to damage in the summer, when they are already hot, from overcharging. If the batteries are too warm to accept what the PV array can produce this power is lost unless diverted to a useful purpose. My C-40 came with a temp probe for the batteries and I use it.
If you have the land and the resources I suggest you look into adding some wind to your system. Start small if you have to, but the winds here are most pronounced in the fall until spring. Just when the sun becomes less reliable our windy season starts. Wind blows at night. Wind works.
Hope these ramblings help in some way,
