5 ms·

> The overwhelming majority of Texas homes are outfitted with electric heaters that are the technological equivalent of a toaster oven. During the most severe c

by comex 5y ago

> The overwhelming majority of Texas homes are outfitted with electric heaters that are the technological equivalent of a toaster oven. During the most severe cold fronts, residents crank up those inefficient units[..] What does this mean? I thought all electric heaters were essentially 100% efficient, due to conservation of energy.

dragonwriter 5y ago
> I thought all electric heaters were essentially 100% efficient, due to conservation of energy. Well, gas heaters are a lot more than 100% efficient in terms of heating per unit of electricity consumed, so better for the grid. (Before anyone else points it out, yes, electric heat pumps are usually more than 100% efficient, too, but that's not relevant here because in severe cold, they are less efficient than direct heating.)
- tialaramex 5y ago
  Air source heat pumps aren't efficient in extremely cold outside air, and so you're back to resistive heating - but for ground source you should see very little change, because the temperature of the rock under you doesn't change suddenly on a cold day. If we have a century of cold weather the rock will cool down, but one particularly icy week won't do it. The ground effectively is your heat battery, pump heat into it in summer (removing it from your home), pump heat back out in winter (to heat your home up).
  - bluGill 5y ago
    This is Texas we are talking about. What they consider extreme cold is still within a modern heat pump's useful range. If this was about northern Canada or other such climates you would have a good point.
- c_o_n_v_e_x 5y ago
  ..and when a heat pump isn't moving enough heat / hitting set point inside the home, emergency heat (electric heat strips) is activated.
- Mvandenbergh 5y ago
  ASHPs are still well above 100% at the kind of temperatures reached in Texas during this period.
- tzs 5y ago
  Cold-weather residential heat pumps have gotten a lot better in the last 10 years or so. Mitsubishi's residential air-source ductless mini-split heat pumps that have their "Hyper-heating inverter" technology are greater than 100% down to at least -13℉ (-25℃), although their capacity starts dropping fairly linearly from 100% at 23℉ (-5℃) to 76% at -13℉ (-25℃), so unless you oversized your system a bit you might have to put up with your house being a few degrees cooler when it gets very cold outside for a long time. Their efficiency remains above 180% down to around -5℉ (-20℃). In most of the major cities of Texas these would have worked fine and remained around 200% or higher efficiency and around 90% capacity. Only a small number of people would have had them get down to 100% efficiency. Fujitsu and Daikon have similarly performing heat pumps.
  - sidewndr46 5y ago
    That's interesting to know. I had this heat pump in Florida that couldn't keep up with an external temperature of 49 F. That kind of made decide they were useless. Maybe if at some point in the future I have to buy a unit I will reconsider it.
    - mrguyorama 5y ago
      Recently the guy from Technology Connections on YouTube made a very good point: Consider technology and tools as they are now, not as you last disliked them.
fy20 5y ago
It's not any more efficient, but there is actually a technology that has been around for a while which lets you store heat energy during off-peak hours and use it during peak hours: electric storage heaters. They look like large baseboard heaters, and inside have a bunch of ceramic bricks which can store a lot energy. During off peak periods the heaters can 'charge', i.e. heat up the bricks, then after that the heat is slowly released over time. Modern versions have a small fan to assist releasing heat, controlled by a thermostat or other smarts. The thing is though, these can store a lot of energy. My parents had a new one installed last year which stores 24 kWh of heat: https://www.elnur.co.uk/product/ecombi-hhr-high-heat-retention-storage-heaters/ https://www.elnur.co.uk/product/ecombi-hhr-high-heat-retenti... Potentially these (the charging can be controlled by a smart meter) could have reduced the electricity demand during peak times.
megaman821 5y ago
Gas furnaces are about 95% efficient. Burning gas at a power plant, transmitting to your home, and then producing heat with an electric heater is nowhere near that. What is striking to me, is that roughly 50% of Texas have gas furnaces and most of the rest have electric resistance heating. Nearly everyone has an AC. There was more demand for electricity from those using electric heaters during the cold snap than in the summer from AC's when the state has an average temperature near a hundred. It would probably be worth it to subsidize a heat pump for anyone stuck with resistance heating.
- bluGill 5y ago
  When the temperature is at 100 and you want your house at 70 there is a 30 degree difference. When the temperature is 30 and you want your house at 70 there is a 40 degree difference. Even with heat pumps (which are a good idea) you need more power to handle larger temperature differentials.
  - pandaman 5y ago
    Yes, but the comparison is not between the AC and a heat pump, but between an electric resistance heater and a heat pump. Heat pump's COP is greater than 100% as it takes less energy to heat the air inside than the energy of the heated air while a resistance heater is 100% so is less efficient. In other words: a 10K Watt resistance heater will consume 10 KWh in an hour, a 10K Watt heat pump will consume 2-5 KWh over the same time depending on the temperatures and construction.
- pandaman 5y ago
  I think it's the root of the problem: when you are running your 10K Watt resistance heater full blast it's very likely that every neighbor is doing the same at the same time (both because it's also cold for them and they also have electric heat as the whole neighborhood probably does not have a gas line).
MadeThisToReply 5y ago
Depends how you generate the electricity that powers the heaters. If it's coming from fossil fuels (as most of it does), it's obviously inefficient: you're burning fuel to generate heat, then using the heat to generate electricity, then using electricity to generate heat again. Far simpler to just burn the fossil fuel for heat directly.
totalZero 5y ago
100% is not a hard cap on the efficiency of a heater. For example, geothermal electric heat pumps typically achieve greater than 300% efficiency in terms of thermal energy delivered per electric energy consumed.

by comex 5y ago

dragonwriter 5y ago

> I thought all electric heaters were essentially 100% efficient, due to conservation of energy. Well, gas heaters are a lot more than 100% efficient in terms of heating per unit of electricity consumed, so better for the grid. (Before anyone else points it out, yes, electric heat pumps are usually more than 100% efficient, too, but that's not relevant here because in severe cold, they are less efficient than direct heating.)

tialaramex 5y ago
Air source heat pumps aren't efficient in extremely cold outside air, and so you're back to resistive heating - but for ground source you should see very little change, because the temperature of the rock under you doesn't change suddenly on a cold day. If we have a century of cold weather the rock will cool down, but one particularly icy week won't do it. The ground effectively is your heat battery, pump heat into it in summer (removing it from your home), pump heat back out in winter (to heat your home up).
- bluGill 5y ago
  This is Texas we are talking about. What they consider extreme cold is still within a modern heat pump's useful range. If this was about northern Canada or other such climates you would have a good point.
c_o_n_v_e_x 5y ago
..and when a heat pump isn't moving enough heat / hitting set point inside the home, emergency heat (electric heat strips) is activated.
Mvandenbergh 5y ago
ASHPs are still well above 100% at the kind of temperatures reached in Texas during this period.
tzs 5y ago
Cold-weather residential heat pumps have gotten a lot better in the last 10 years or so. Mitsubishi's residential air-source ductless mini-split heat pumps that have their "Hyper-heating inverter" technology are greater than 100% down to at least -13℉ (-25℃), although their capacity starts dropping fairly linearly from 100% at 23℉ (-5℃) to 76% at -13℉ (-25℃), so unless you oversized your system a bit you might have to put up with your house being a few degrees cooler when it gets very cold outside for a long time. Their efficiency remains above 180% down to around -5℉ (-20℃). In most of the major cities of Texas these would have worked fine and remained around 200% or higher efficiency and around 90% capacity. Only a small number of people would have had them get down to 100% efficiency. Fujitsu and Daikon have similarly performing heat pumps.
- sidewndr46 5y ago
  That's interesting to know. I had this heat pump in Florida that couldn't keep up with an external temperature of 49 F. That kind of made decide they were useless. Maybe if at some point in the future I have to buy a unit I will reconsider it.
  - mrguyorama 5y ago
    Recently the guy from Technology Connections on YouTube made a very good point: Consider technology and tools as they are now, not as you last disliked them.

fy20 5y ago

It's not any more efficient, but there is actually a technology that has been around for a while which lets you store heat energy during off-peak hours and use it during peak hours: electric storage heaters. They look like large baseboard heaters, and inside have a bunch of ceramic bricks which can store a lot energy. During off peak periods the heaters can 'charge', i.e. heat up the bricks, then after that the heat is slowly released over time. Modern versions have a small fan to assist releasing heat, controlled by a thermostat or other smarts. The thing is though, these can store a lot of energy. My parents had a new one installed last year which stores 24 kWh of heat: https://www.elnur.co.uk/product/ecombi-hhr-high-heat-retention-storage-heaters/ https://www.elnur.co.uk/product/ecombi-hhr-high-heat-retenti... Potentially these (the charging can be controlled by a smart meter) could have reduced the electricity demand during peak times.

megaman821 5y ago

Gas furnaces are about 95% efficient. Burning gas at a power plant, transmitting to your home, and then producing heat with an electric heater is nowhere near that. What is striking to me, is that roughly 50% of Texas have gas furnaces and most of the rest have electric resistance heating. Nearly everyone has an AC. There was more demand for electricity from those using electric heaters during the cold snap than in the summer from AC's when the state has an average temperature near a hundred. It would probably be worth it to subsidize a heat pump for anyone stuck with resistance heating.

bluGill 5y ago
When the temperature is at 100 and you want your house at 70 there is a 30 degree difference. When the temperature is 30 and you want your house at 70 there is a 40 degree difference. Even with heat pumps (which are a good idea) you need more power to handle larger temperature differentials.
- pandaman 5y ago
  Yes, but the comparison is not between the AC and a heat pump, but between an electric resistance heater and a heat pump. Heat pump's COP is greater than 100% as it takes less energy to heat the air inside than the energy of the heated air while a resistance heater is 100% so is less efficient. In other words: a 10K Watt resistance heater will consume 10 KWh in an hour, a 10K Watt heat pump will consume 2-5 KWh over the same time depending on the temperatures and construction.
pandaman 5y ago
I think it's the root of the problem: when you are running your 10K Watt resistance heater full blast it's very likely that every neighbor is doing the same at the same time (both because it's also cold for them and they also have electric heat as the whole neighborhood probably does not have a gas line).

MadeThisToReply 5y ago

Depends how you generate the electricity that powers the heaters. If it's coming from fossil fuels (as most of it does), it's obviously inefficient: you're burning fuel to generate heat, then using the heat to generate electricity, then using electricity to generate heat again. Far simpler to just burn the fossil fuel for heat directly.

totalZero 5y ago

100% is not a hard cap on the efficiency of a heater. For example, geothermal electric heat pumps typically achieve greater than 300% efficiency in terms of thermal energy delivered per electric energy consumed.