Nick
The most efficiency gains will be realized by proper insulation. Everyone is correct on this. I think Iowa is known for getting pretty cold in the winter, and hot in the summer.
Electric heaters, as Rod pointed out, are technically the most efficient heat devices you can use, but they're also the most costly to operate depending on your location.
I think the most efficient propane heater run in the mid 80 percent range and #2 fuel oil furnaces can be in the low to mid 90's. There are some more efficient propane systems, but very costly to install.
If you have Natural Gas to your house that would be my very first choice.
Last edited by Mike Cutler; 05-17-2015 at 5:49 PM.
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