heating with oil is expensive. solar panels actually can heat well. just heat a block of concrete. the concrete is the battery. electrodacus is doing this now.
Burning natural gas is among the cheapest forms of heating we have, and it works 24/7/365 and at all latitudes. Solar heating using a slab as a heat reserve requires re-engineering houses completely and may be impossible in a lot of places that don't get a lot of sun during the coldest months.
sure, nat gas works great where lines go to your house. I was at a house in the seattle area last weekend (a well developed metropolis) where people had propane. Solar goes everywhere, but depends on good weather to be useful.
Perfect statement of someone who more than likely lives within a city with public utilities. However, there are actually a large amount of people in rural U.S. that have to use either Oil or Electric heating (in which both are expensive). In These rural area's, Oil heating is the norm and in order to convert to an electric heat there are extensive cost's involved (which most people in these area's cannot afford). Living in a city (especially west-coast) has certain amenities that the rest of the U.S. does not. Complete solar power in rural Wisconsin or the Dakota's for example isn't a real viable option. There is much less sunless then the west coast and extreme season weather changes (humidity, rain, snow, hot/cold).
Also need to design and build with materials that maintain as constant a temperature as possible. Double glazing, insulated walls, floors and roofs, orientation to the sun etc.