Entirely apart from the high cost of electric resistance heat, (that is, regardless of heat source) a 1969 house is almost certainly going to benefit from insulation upgrades and the boring best bang-for the buck stuff nobody ever thinks is "fancy enough" to go for first - caulking, weatherstripping, and generally reducing air leakage.

With the advent of cold-climate air-air heat pumps (mini-splits) that is probably the best direction to look for electric heat replacement - 2.2-3.5 times as much heat from the same amount of electricity. But start with a caulking gun and a can or 12 of spray foam, follow that with more insulation anywhere you can add it (usually the attic) - THEN think about replacing the heating units, since it's unlikely you'll actually get that done during this heating season, while you can be air-sealing in minutes and benefiting from it in minutes - not to mention it's cheap...

Solar electric panels generally don't make sense as a heat source. Direct collection of heat from the sun is far more efficient than collecting a little bit of the suns energy as electricity and then using that for heat. Costs of the relevant types of panels are also rather different.