Adults generate roughly 400 to 600 BTUs per person/hour, depending on their size. So I suggest you invite lots of people over in winter, after supper of course. In summer, you visit them.
I would also have a sealed door between upstairs and downstairs and basement. Control and/or timer both your heaters depending on activity. Check seals on windows, seal the fireplace flue if you are 100% electric. Wear heavier clothing, but I don’t go less than 55 - 60F, it’s a little too uncomfortable. On the bright side, if you are shivering all the time you are burning cals and will need to eat more. Life is a trade-off.
Just imagine how warm the house would be if you fed everyone beans.