My residential central air system started making horrid noises, and had unreliable gas ignition... Probably just needed massive cleaning, but there was a connection charge whether I used any gas or not, and... my increased electric usage is close to what that would have cost, and isn't likely to blow me up. So I quit using it, and will eventually remove it. The AC (in hot and humid St. Louis) is a single LG window unit that is some sort of "dual inverter" thing... It was on all summer in the rear bedroom (shotgun house), kept the whole house livable, and my highest electric bill was $135ish... I figure cost/month in the heat was about $60ish... If the house was bigger, I'd buy a second one. Winter-wise, I have a couple of the oil-filled radiator space heaters - I set them to the lowest wattage, and just let them go after things get reliably under freezing. Cheap then... House generally stays around 55 (which I prefer), and when it gets REALLY cold, I add a third one - also set for just a few hundred watts. All on different circuits. One of them is on a dreaded extension cord. A 10 gauge extension cord... Planning purchase of a pellet stove in the spring after I can figure out how to plumb the chimney...