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I've heard several times that electrical heaters of any kind are expensive and much less efficient than other heat sources and I feel like I am throwing money o

I've heard several times that electrical heaters of any kind are expensive and much less efficient than other heat sources and I feel like I am throwing money out of the window when I turn them on. This doesn't make any sense to me though. Can someone with a better understanding of physics than me explain to me why this would be the case? I would imagine electricity to be just about the most efficient way to transfer energy. And furthermore, as I understand it, lost energy tends to become heat!

dec0dedab0de 8y ago
Because in order to get the electricity to your house the power plant had to first do whatever it needed to do to generate the electricity. for example if the power plant is burning oil, and converting that to electricity, then you convert that electricity to heat you're going to get much less heat than just burning the oil yourself.
- dragonwriter 8y ago
  > for example if the power plant is burning oil, and converting that to electricity, then you convert that electricity to heat you're going to get much less heat than just burning the oil yourself. OTOH, the power plant probably has a rail connection or pipeline for oil, and the marginal energy cost of transporting an additional unit of oil to the power plant is probably quite low compared to the marginal energy cost of transporting the same additional unit of oil to your house.
  - dec0dedab0de 8y ago
    I'm not sure about that. I usually get about 125 gallons at a time. And since heating oil is just diesel with dye in it, we can just add deliver costs in gallons. Even assuming im the only delivery, I doubt it would take more than a gallon of gas to travel to my house. But to be safe lets say 5. With the above assumption, the question is Could 130 gallons burned at a power plant generate more heat in my house via electricity. Than 125 gallons burned in my house directly. I dont know enough to give an answer but my gut says no.
    - dragonwriter 8y ago
      Oh, I'm not saying distribution efficiencies necessarily outweigh transmission losses, just that if you weigh the cost of getting energy from the place to your house you should also make sure you consider the cost of getting fuel to each location.
  - bluGill 8y ago
    While technically correct, this is the wrong way to look at it. The energy density of oil is large, so transmission losses per unit of energy is low. Any modern house furnace will be at least 80% efficient, and 96% isn't unheard of. The most fuel efficient power plants are around 60%, (combined cycle coal plants) but any plant running oil is probably less, plus you have all the transmission losses for electric (8%). In the end if you are burning fuel for heat it is both cheaper and a better use of energy to burn it locally. Of course that isn't the full picture either. Electric can come from many sources (wind, PV), and scale means they can mix sources cheaper. (imagine a coal furnace, gas furnace, oil furnace, PV heat, and a windmill all at your house - it is obviously ridiculous, but large utilities have this) You also don't have to burn for heat directly. Electric leaves open the option of a heat pump which can be >100% efficient when it isn't too cold.
  - buttcoinslol 8y ago
    >OTOH, the power plant probably has a rail connection or pipeline for oil, and the marginal energy cost of transporting an additional unit of oil to the power plant is probably quite low compared to the marginal energy cost of transporting the same additional unit of oil to your house. Uh, I have a natural gas pipe coming directly into my home, along with nearly everyone in my state, and also region. Electric heating is more efficient than natural gas, but electricity is more expensive per BTU, at least where I live.
krapht 8y ago
Natural gas delivers more heat per dollar spent.
MaulingMonkey 8y ago
> And furthermore, as I understand it, lost energy tends to become heat! AFAIK the whole problem is that "waste" heat happens at the coal/gas plant where heat is converted into electricity in the first place, and (to a lesser extent?) in the transmission lines, not at your house where it'd be useful.
- kristiandupont 8y ago
  Ok, this I can understand. If the cost is in fact in the initial conversion rather than in transportation, it makes sense. In that case though, we are not nearly as good at turning heat into electricity as I thought.
  - MaulingMonkey 8y ago
    http://insideenergy.org/2016/06/20/ie-questions-can-we-turn-power-plants-wasted-heat-into-power/ http://insideenergy.org/2016/06/20/ie-questions-can-we-turn-... is an interesting read. The efficiency of a basic coal plan is pretty dismal - converting a mere third of the released heat into useful electricity if I'm understanding right. And even if you build a state of the art combined heat & power system (requiring steam pipes to heat houses, not just electric lines) we're still looking at only ~85% efficiency.
semi-extrinsic 8y ago
The thing about electricity is that it's perhaps the most "useful" form of energy. Not only can you use it to heat your house, but also to drive your car or run your phone or your power tools etc. On the other end of the spectrum, you have "low grade waste heat", take for instance the heat from running a computer. Almost all the (useful) energy input as electricity gets turned into hot air coming out. You can use that to heat your room, but nothing else. So because electricity is so useful and high grade energy, we prefer not to use it "just" for resistive heating. Running heat pumps is an example of a much better use (you can get 4-5 times as much heat out).
- kristiandupont 8y ago
  >you can get 4-5 times as much heat out [...] ..but why? The second law of thermodynamics says that the amount of energy won't change, it can only change form, right? (Correct me if I'm wrong, I'm not sure). So the electricity should either remain electricity or turn into heat? I get that it might not happen at the place where we want it to. For instance, we don't want to be heating up the ground between the power plant and my house where the cable runs. And I also get that turning heat into electricity (as it happens at the power plant) might not be efficient. But I still feel that it should perform better than running a pipe with hot water which seems more likely to leak heat into the ground along the way.
  - semi-extrinsic 8y ago
    >>you can get 4-5 times as much heat out [...] > ..but why? Because you are literally pumping heat from outdoors to indoors. You are reducing the energy of the outdoor air and increasing the energy of the indoor air. The electric energy spent is used to drive a motor that is pumping a fluid round in a loop. The pump is placed where you go from outdoors to indoors. Opposite the pump in the loop, you have a pressure reduction valve, and together these give you a higher fluid pressure on the indoor side, say 40 bar vs 20 bar. The trick is that this pressure difference means that the low pressure fluid is also cold, so it can be heated by the outside air, and the high pressure fluid is warm, so it can release heat to then indoor air. The thing about running hot water (e.g. district heating) is because you use heat that is literally free. E.g. if you have a waste incineration plant burning all the garbage, that's a lot of free heat. Or if you have a big data centre, lots of waste heat. Let's use it! In systems like the OP post, the water acts as both energy storage and a convenient way to distribute heat. No DC/AC inverter, etc.

dec0dedab0de 8y ago

Because in order to get the electricity to your house the power plant had to first do whatever it needed to do to generate the electricity. for example if the power plant is burning oil, and converting that to electricity, then you convert that electricity to heat you're going to get much less heat than just burning the oil yourself.

dragonwriter 8y ago
> for example if the power plant is burning oil, and converting that to electricity, then you convert that electricity to heat you're going to get much less heat than just burning the oil yourself. OTOH, the power plant probably has a rail connection or pipeline for oil, and the marginal energy cost of transporting an additional unit of oil to the power plant is probably quite low compared to the marginal energy cost of transporting the same additional unit of oil to your house.
- dec0dedab0de 8y ago
  I'm not sure about that. I usually get about 125 gallons at a time. And since heating oil is just diesel with dye in it, we can just add deliver costs in gallons. Even assuming im the only delivery, I doubt it would take more than a gallon of gas to travel to my house. But to be safe lets say 5. With the above assumption, the question is Could 130 gallons burned at a power plant generate more heat in my house via electricity. Than 125 gallons burned in my house directly. I dont know enough to give an answer but my gut says no.
  - dragonwriter 8y ago
    Oh, I'm not saying distribution efficiencies necessarily outweigh transmission losses, just that if you weigh the cost of getting energy from the place to your house you should also make sure you consider the cost of getting fuel to each location.
- bluGill 8y ago
  While technically correct, this is the wrong way to look at it. The energy density of oil is large, so transmission losses per unit of energy is low. Any modern house furnace will be at least 80% efficient, and 96% isn't unheard of. The most fuel efficient power plants are around 60%, (combined cycle coal plants) but any plant running oil is probably less, plus you have all the transmission losses for electric (8%). In the end if you are burning fuel for heat it is both cheaper and a better use of energy to burn it locally. Of course that isn't the full picture either. Electric can come from many sources (wind, PV), and scale means they can mix sources cheaper. (imagine a coal furnace, gas furnace, oil furnace, PV heat, and a windmill all at your house - it is obviously ridiculous, but large utilities have this) You also don't have to burn for heat directly. Electric leaves open the option of a heat pump which can be >100% efficient when it isn't too cold.
- buttcoinslol 8y ago
  >OTOH, the power plant probably has a rail connection or pipeline for oil, and the marginal energy cost of transporting an additional unit of oil to the power plant is probably quite low compared to the marginal energy cost of transporting the same additional unit of oil to your house. Uh, I have a natural gas pipe coming directly into my home, along with nearly everyone in my state, and also region. Electric heating is more efficient than natural gas, but electricity is more expensive per BTU, at least where I live.

krapht 8y ago

Natural gas delivers more heat per dollar spent.

MaulingMonkey 8y ago

> And furthermore, as I understand it, lost energy tends to become heat! AFAIK the whole problem is that "waste" heat happens at the coal/gas plant where heat is converted into electricity in the first place, and (to a lesser extent?) in the transmission lines, not at your house where it'd be useful.

kristiandupont 8y ago
Ok, this I can understand. If the cost is in fact in the initial conversion rather than in transportation, it makes sense. In that case though, we are not nearly as good at turning heat into electricity as I thought.
- MaulingMonkey 8y ago
  http://insideenergy.org/2016/06/20/ie-questions-can-we-turn-power-plants-wasted-heat-into-power/ http://insideenergy.org/2016/06/20/ie-questions-can-we-turn-... is an interesting read. The efficiency of a basic coal plan is pretty dismal - converting a mere third of the released heat into useful electricity if I'm understanding right. And even if you build a state of the art combined heat & power system (requiring steam pipes to heat houses, not just electric lines) we're still looking at only ~85% efficiency.

semi-extrinsic 8y ago

The thing about electricity is that it's perhaps the most "useful" form of energy. Not only can you use it to heat your house, but also to drive your car or run your phone or your power tools etc. On the other end of the spectrum, you have "low grade waste heat", take for instance the heat from running a computer. Almost all the (useful) energy input as electricity gets turned into hot air coming out. You can use that to heat your room, but nothing else. So because electricity is so useful and high grade energy, we prefer not to use it "just" for resistive heating. Running heat pumps is an example of a much better use (you can get 4-5 times as much heat out).

kristiandupont 8y ago
>you can get 4-5 times as much heat out [...] ..but why? The second law of thermodynamics says that the amount of energy won't change, it can only change form, right? (Correct me if I'm wrong, I'm not sure). So the electricity should either remain electricity or turn into heat? I get that it might not happen at the place where we want it to. For instance, we don't want to be heating up the ground between the power plant and my house where the cable runs. And I also get that turning heat into electricity (as it happens at the power plant) might not be efficient. But I still feel that it should perform better than running a pipe with hot water which seems more likely to leak heat into the ground along the way.
- semi-extrinsic 8y ago
  >>you can get 4-5 times as much heat out [...] > ..but why? Because you are literally pumping heat from outdoors to indoors. You are reducing the energy of the outdoor air and increasing the energy of the indoor air. The electric energy spent is used to drive a motor that is pumping a fluid round in a loop. The pump is placed where you go from outdoors to indoors. Opposite the pump in the loop, you have a pressure reduction valve, and together these give you a higher fluid pressure on the indoor side, say 40 bar vs 20 bar. The trick is that this pressure difference means that the low pressure fluid is also cold, so it can be heated by the outside air, and the high pressure fluid is warm, so it can release heat to then indoor air. The thing about running hot water (e.g. district heating) is because you use heat that is literally free. E.g. if you have a waste incineration plant burning all the garbage, that's a lot of free heat. Or if you have a big data centre, lots of waste heat. Let's use it! In systems like the OP post, the water acts as both energy storage and a convenient way to distribute heat. No DC/AC inverter, etc.