Why is combustion cheaper than electricity to run when it comes to heating but not when it comes to transportation?
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In transportation, you are converting the energy of the fuel into kinetic energy to move you. This is really inefficient due to size limitations of engines. 25-30% of the energy in fuel is actually used to move you forward. The rest is wasted as heat. Electric motors are 80-90% efficient, so they are much better at converting the electrical energy into motion. Not to mention, energy in the fuel is wasted when you are idling at a light or using your brakes, since the energy you spent accelerating is lost as brake heat while slowing down. Electric cars do not idle at lights. They also use the electric motors to generate electricity to slow the vehicle down, recovering a decent amount of energy spent accelerating the car. This is called regenerative braking and is used in hybrids as well.
In home heating, that waste heat in the fuel is what you actually want, so furnaces burn it at a 90+% efficiency, capturing most of the chemical energy in the fuel. This puts it much more on par with electricity, which is 100% efficient since all the electrical energy is spent on heating up a wire. At that point it comes down to the cost of fuel, which is cheaper for propane/natural gas.
However, there are heat pumps available to heat your home using the refrigeration cycle. They are basically air conditioners that can run in reverse. They are over 100% efficient, meaning if you spend 100 watts of electricity to run the heat pump, you’ll get 200-300 watts of heat energy out of it. This is possible because they do not generate heat like furnaces and heaters. They move heat from outside your house to inside. This can be cheaper than fuel furnaces, though they have some limits unless you spend for top-of-the-line cold weather units.
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