Why is combustion cheaper than electricity to run when it comes to heating but not when it comes to transportation?
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When you’re heating a house using gas, you get 80%+ of the potential energy out of that gas. An internal combustion engine gets 30-35% of the potential energy out of its gas.
This is because most of the energy that we get out of gas is heat, and your HVAC system is very good at taking that heat and distributing it throughout your house. On the other hand, your car doesn’t want a lot of heat. That’s a crummy byproduct that we want to get rid of, and only a portion of the potential energy is captured by the car to be used for movement.
Additionally, combustion cars have to maintain some minimum RPM or they stall out. This means that even when they’re at a complete stop, which happens a lot in cities, it is still burning fuel just to keep the engine spinning and ready to go when the light turns green. An electric car that comes to a stop can just have its engine turn completely off until it’s ready to go. This significantly increases its actual energy use per trip in comparison to a combustion engine.
Car engines are very inefficient, discharging a lot of the energy produced from combustion as heat.
At home, that wouldn’t really mean anything as heat is the desired product of burning fuels.
Electric energy generally costs more than fossil fuel energy. Since producing heat is nearly 100% efficient heating with cheaper energy (like gas) is cheaper.
However for cars, while gas is cheaper on a per energy basis, engines are not efficient so it takes a lot more energy for an internal combustion car to drive a mile than it would for an EV to drive that same mile. For the energy in one gallon of gas an IC vehicle can drive maybe 25 miles while an EV can drive 120 miles. Even if the electrical energy costs more its far cheaper to drive the EV because it uses far less of it.
Edit: Also that is resistive electric heating, electric heating with heat pumps is more efficient than fossil fuel heating both in terms of energy in/heat out and total emissions. https://www.nature.com/articles/s41893-020-0488-7
Also, in some areas where your electricity in generated from clean sources and there is plenty of it, heat from electricity is MORE efficient than gas. Gas is more efficient if electricity comes from a dirty source. So, “it depends”.
I might be misunderstanding your question but from a manufacturing point of view an electric car is very simple. It doesn’t need a complex engine, transmission with variable gearing, etc. The expensive portion is just the battery. An internal combustion car however has a lot of complexity to work efficiently but we make a lot of them and have been doing that for a long time so we have gotten very good at it.
At home however it is a different story. We don’t need to run an engine for heating that is done at the power station. We also don’t need to run a complex internal combustion engine to make mechanical power we are just making heat. It is very simple to do either electrically or by burning natural gas so all that really matters is how expensive the electricity or the gas is. The gas is very cheap compared in many countries.
Lets say it takes 10kwh of energy to drive a car.
Petrol has a lot of energy. That’s awesome, however the primary output of combusting petrol is heat. So much so that only ~30% of the available energy in the petrol is being used to actually move the car. So to drive the car, we need to feed it 34kwh of petrol to get out the 10kwh we need to actually move the car.
Electricity/electric car motors are way more efficient at that. They can be around 85% efficient. So to get the same 10 kwh to drive the car, we only need to give it ~12kwh of electricity. That is why electric cars can accomplish the same thing with less energy and are more energy efficient.
Electric heating is more expensive than gas, because gas has a lot of energy in it, and if your goal is to just convert that energy to heat, gas does that really well. Electricity can accomplish the same thing, but it just takes a lot more of it, since converting energy to heat is super efficient for both electric and gas.
I don’t know the answer or really understand the question but no one has mentioned that we use gasoline for cars and natural gasses for homes and I feel like that has to be some kind of factor? Like I said though, I have no idea…
Because making heat and pushing a car down the road are two very different end results. Petrol/diesel car engines are not very efficient and waste about 75% of their fuel energy just making heat instead of moving the vehicle.
If all you want is heat, then that works fine. Just burn the fuel and you get tons of heat from an energy dense fuel.
Electricity storage and generation is not very energy dense, but we have electric motors that are +90% efficient, so it’s great for moving things like cars, but not great for heating because when compared to how much energy is in liquid fuel, you can’t generate or move an equivalent amount of electricity very easily, so makes less sense to just convert that electric energy into heat unless it’s your only option.
Because of the energy types and mechanisms.
– Natural gas is cheaper than oil.
– Combustion engines lose a ton of energy to heat, rather than it all becoming mechanical energy.
– Electric engines are great at converting to electrical energy into mechanical energy.
– To create heat with natural gas, you just need a spark and some oxygen, and you are unlocking the energy that is already stored in the gas.
– To create heat from electricity, you have to convert the electricity into a new form of energy.
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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