Single furnace distributes forced air heat unevenly. Second floors are hotter, first floors are cooler.
Multiple systems distribute radiant heat evenly. Floors heated to warm the areas that are needed.
Take a look at the opportunity cost by going with a forced air distribution method through ductwork. Likely, the warmth that your air handler, or furnace, is distributing is also overcompensating since the insulation of your windows degrades over time.
If you're not using a programmable or smart thermostat you could be loosing up to 18% in savings when using a forced air system.
Finally, the Annual Fuel Utilization Efficiency (AFUE) of your gas furnace combined with air losses at the cabinet can contribute up to 6% more to your energy footprint (not bills).
This case study tackles the Hybridization of gas and electrical sources, with a discussion on Beneficial Electrification, and finding on capital cost, energy savings and reduction of GHG emissions vis-a-vis various technologies. With electrical resistance as a main heating distribution method, a home can pair this with standby forced-air using an Air Source Heat Pump (ASHP).