Power source at remote, high elevation, cold location.

However you can manage it, true deep cycle flooded cell lead acid batteries must be kept from freezing. Optimum performance happens between 70 and 80 degrees Fahrenheit. Remember that batteries convert electrical energy into a chemical energy and this is whats stored.

120 multiplied by 3 equals 360. Assuming that the load is constant for 24 hours a day that equates to a 8640 watt hour day. Divided by a nominal battery voltage of 48 this would equate to nothing less than 180 amp hours of storage. 8640 divided by 4 hours of equivalent full rated charge this would be nothing less than a 2160 watt PV array. (One could supply ample power for a modest home with that.) It would be curious if you have not considered building an enclosure for this exposed water supply pipe. Maybe something along the lines of a small insulated greenhouse. This would reduce the need for a heat tape to run 24/7. Or if a "waterjacket" could be created around the pipe to store heat for use at night, as well it might incorporate a small vdc element greatly reducing the size of the batterybank and PV array. Or if possible cover it with a goodly amount of wood chips and cover that with black tarp. Or... well it always comes back to this with me, mankind managed to survive on the planet Earth for thousands of years without utilizing electrical energy. We are testimony to that fact. It would seem that in only the last 100 years we have devolved to a place where we cannot survive without the utilization of electrical energy. Pity about Earth.

I would appear as though your thinking about using the well as a means of electric power generation. Is it an artesian well?