We have two AC units and two electric furnaces. Not as efficient as gas furnaces, but they also don't have to work like the one we had in Wisconsin. Does the neighbor just like it really cold? I wondered. Then I looked it up online, and I found that he has a heat pump rather than an air conditioner. I mean, really, it IS an AC that also has the ability to somehow reverse what it does to pump warm air into the house in winter. I don't claim to understand the physics of the whole thing, but it's a thing in the South.
Of course, I had to wonder: if heat pumps are claimed to be more efficient than an electric furnace, why isn't it an option I've ever heard of coming from the North? Actually, the more I read, the more I found that people can use heat pumps, even in Wisconsin, but it's probably a seemingly silly extra unit to worry about, since you NEED the gas heater on top of it...installation costs for a heat pump are 20 times more than a heater (Wikipedia--seems too much?), and that's a big investment to get the benefits of 2 to 3 times more efficient heat than an electric heater, and mostly less efficient than natural gas.
Heat pumps would be mostly all you'd ever need in Florida, since the units remain more efficient than electric furnaces to 0 degrees or lower. I found another website that said that gas furnaces are more efficient beginning at around 65 degrees, or basically always, even though a manufacturer website implied this was not the case (but I would too if I could sell more heat pumps). However, how many heating days below 65F do we get in NE Florida? Probably enough to warrant gas heat instead of a heat pump, if it's available, since it's cheaper to install and more efficient to run almost as soon as heat is needed. But you'll really need a consistent source of heat for about two months in Jacksonville, so a homeowner is planning the reverse of Wisconsin, where we needed AC consistently for about that much time.
Electric or propane is more complicated. I have a propane fireplace, but it's more for looking at the oddly blue flame than for heat. Heat pumps stay more efficient than electric heaters pretty much down to Absolute Zero, and they're probably better than propane to the range of what Florida would deem apocalyptically low lows, but it still costs more to install, so you would have to consider how long the unit would last, etc. While the propane might be more efficient than the electric furnace for one room, there's no way my little fireplace will heat the whole house, and I don't really want to refill the tank several times at Uhaul, so I'll treat it more as a bonus heat source / place to roast hot dogs.
