66F is ridiculously cold to me, and I live in Canada where it can reach -40(F or C) in the winter. I would find that very uncomfortable and elderly people would be shivering constantly and highly susceptible to respiratory illness.

I have a modern cold climate air source heat pump which essentially needs to run 24 hours a day to maintain a stable 20C when the outdoor temperatures reach -15C. Below that, the heat pump shuts off and the furnace kicks in to provide emergency heating. My thermostat is a modern one with full time-of-day and day-of-week scheduling for heating and cooling, but it doesn't matter because the heat pump by itself is not able to swing the temperature up (by even half a degree) on its own, so this causes the furnace to kick in every time the schedule calls for a higher temperature, defeating the entire purpose of time-of-day scheduling.

I will also add that where I live (Southern Ontario) the sky is overcast 90% of the time during the winter. Solar panels, even somehow free of snow and ice, are going to produce almost nothing on those dark days. Add in the need to keep the panels free of snow and ice (presumably with heating, since nobody is going to be climbing around on their roof in the winter), and you'd likely reach energy net-negative trying to make use of them.