An All Electric house is a joke for 98% of the US that live in areas
north of zone 8 as electricity is double the cost per BTU for most.
If heating season is expensive unless you have subsides Hydro, gas is
the cheapest.

If OP is looking for total replacement gas units are up to 94.5%
efficient, that is higher than oil units go.

OK

Can one also cool and use AC using gas as the energy source?

Just curios