If you have a fireplace but do not use it you should figure out a way to seal it up so that the heat in your home doesn't get sucked out of the chimney. The other option is to get a wood stove fireplace insert, if you have the money to do so. Once you learn how to build a proper fire in a wood stove you can load the logs once in the morning and once, maybe twice (in two smaller loads) in the evening so that the stove is constantly producing heat. The downside to an insert though is that you will use electricity to power the fan that is necessary to get the heat into the room.

The best option is a freestanding wood stove stuck in the fireplace , with insulation sealing up the chimney flue. The stove has it's own exhaust liner, so the insulation won't interfere with that. A freestanding stove is best because the radiant heat does not require a fan to move it into the room, although you can purchase fans that are powered by the heat that the stove gives off.

If you buy firewood the cost per BTU is substantially less than oil, propane, or electricity. If you get your firewood for free then you're even better off.

Used wood stoves aren't hard to find. An older model that's in good condition shouldn't be a problem so long as the firebricks are in decent shape and the metal doesn't show any signs of warping.