7 ms·

> The notoriously bad energy efficiency of air conditioners Air conditioners are actually pretty fantastically efficient for what they do. The problem with air

> The notoriously bad energy efficiency of air conditioners Air conditioners are actually pretty fantastically efficient for what they do. The problem with air conditioners is that there's no way to move a ton of heat without using a lot of energy. So, they do use a lot, but they make the most of it. What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air right back out into the environment.

ianai 6y ago
There’s also no obvious market factor incentivizing modernization of old RE let alone efficiency.
eggsnbacon1 6y ago
New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true. Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference. The misconception persists because heat uses gas, which is 5-10X less expensive per BTU of energy than electricity. So it might be cheaper to heat cold areas than run AC in hot ones, but its much more damaging to the environment. Plus, hot climates are using a lot of renewables these days which impacts the environmental friendliness of electric but not gas. I expect migration to the sun belt to accelerate, at least in the US. It makes a lot of sense from environmental perspectives. In some southern cities there's already long stretches every summer where daytime AC use runs on 70%+ renewable energy.
- marcinzm 6y ago
  [I was wrong]
  - roywiggins 6y ago
    Air conditioners are often more than 100% efficient- they move more heat energy than they consume. (Of course if you start with a fossil fuel, turn it into electricity, and then pipe that into an AC unit, the overall efficiency will be dropped by the efficiency of the power plant, but it's still somewhat made up for by the advantages of heat pumps)
    - username505 6y ago
      This is false
      - URSpider94 6y ago
        What is false?
        username505 6y ago
        The total efficiency of an air conditioner will never be more than 100% based on design; you will never be able to remove more heat than what the system produces in net cooling effect based off of the energy consumption created from compression - this is what would lead you to the eventual path of the theory of the heat death of the universe. You may be able to remove heat from one place to another but never more than what the system produces. Heating systems are completely different regarding efficiency.
        tripletao 6y ago
        The ratio of thermal power moved to electrical power input is more properly called "coefficient of performance" rather than "efficiency", but it's far greater than 100% in modern equipment. > From 1990 to 2013, U.S. shipment-weighted efficiency for residential split-system A/Cs increased from 9.5 SEER (~2.2 COP) to 14.9 SEER (~3.8 COP). https://www.energy.gov/sites/prod/files/2016/07/f33/The%20Future%20of%20AC%20Report%20-%20Full%20Report_0.pdf https://www.energy.gov/sites/prod/files/2016/07/f33/The%20Fu...
        URSpider94 6y ago
  - stephen_g 6y ago
    But heat pump heating and cooling has coefficient of performance / energy efficiency ratios around 3-4 (or even higher than 5 for certain applications!), so you more than make back your efficiency loss there.
- dylan604 6y ago
  It is amazing how tight we can make buildings today. I had to learn a lot about HVAC on a remodeling job a few years ago. I had no idea that the drywall can be sealed so tight that when the HVAC system is running it can be next to impossible to open a door without a pressure release duct. Also saw how the HVAC system had vents to bring in air from outside with baffles controlled by the system. Can't remember exact purpose something about helping help control humidity as well as regulation to bring in "fresh" air to mix with the "stale" air in the building. So some parts of construction techniques and building materials have improved significantly. However, when comparing the framing lumber used today to what was used in the 60s, I'm shocked that new construction doesn't fall over the first time the wolf huffs and puffs.
  - sparker72678 6y ago
    The outdoor fresh air intakes are typically via ERVs (Energy recovery ventilation systems). These systems bring in fresh air, filter it, and typically run it through a heat exchanger to minimize energy losses as the fresh air comes and and the stale air goes out. The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous if not cycled regularly.
    - londons_explore 6y ago
      2020: ”Poisonous stuff in our houses... Bad! Let's vent it to the environment!” 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.
      - adrianN 6y ago
        Luckily most organic compounds you find in indoor air aren't very stable.
      - cyberdrunk 6y ago
        > 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe. That's the case in much of the world already... I live in area where there's tons of smog in the colder months and consider installing a system for bringing in filtered air from the outside, so that I won't have to open windows for the 6+ months smog period.
- CarbyAu 6y ago
  Best marketing voice: "Why migrate to the sunbelt? Burn gas and wait for climate change to bring the warmth to you!" ...sigh. I really hope it doesn't go this way.
  - samplatt 6y ago
    Already has, mate. There's no turning back, just a matter of damage mitigation, now.
  - tobyhinloopen 6y ago
    It already has. There is a noticeable shift in temperatures here in the Netherlands. Hot days are getting hotter and much more frequent. Snow is getting rare. We had a yearly ice skating event that never happens anymore because there is no ice. Weeks of 30C weather are getting more common while not long ago, hotter than 25C was considered exceptional. It’s like daily temperatures are just shifted +5 degrees within 2 decades. It’s not just my gut feeling, there are plenty of statistics
    - the-dude 6y ago
      Which yearly event was this?
      - himlion 6y ago
        https://en.wikipedia.org/wiki/Elfstedentocht https://en.wikipedia.org/wiki/Elfstedentocht
        the-dude 6y ago
        This event took place 15 times in the last century. How can this be yearly?
        himlion 6y ago
        I agree it's hardly a yearly event, but this is definitely the even he is referring to. Theoretically yearly would be a better term.
- DoofusOfDeath 6y ago
  > New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I was describing my home renovation project to someone who lives in Brazil. I don't how true this is for that entire country, but she said that it's very uncommon for Brazilian homes to have insulation.
  - fyfy18 6y ago
    This is the same for many homes in Spain and Portugal too. For most of the year it's warm enough outside and you can be comfortable without AC (especially if you are in an older building with thick stone walls), but then for the one or two months of winter it is so cold inside, even though it may only get down to 10C (50F) outside. Most houses rely on resistive electric heaters (if they have any) which end up being very expensive to run. I live in a modern house in Northern Europe, and we don't even turn our heating on until it gets below freezing. Because we have good insulation, only then it starts to drop below 22C (72F) inside.
    - gallegojaime 6y ago
      Completely true, many old homes in Madrid are freezing in the winter. New homes are more regulated in efficiency, however. I lived in a new A-rated flat with sophisticated central heating and thermosolar, paying 500€/mo for the actual home and about 10€/mo for heating.
      - pmontra 6y ago
        Adding to this, I spent a week in a A-rated house. 30+ C outside and I never even looked for the remote of the air conditioner.
- aidenn0 6y ago
  Is NG really over 5X cheaper than electricity? It seems like a NG genset that is better than 20% efficient wouldn't be that hard to build, yet I don't see people running their houses off of electricity that way.
  - kingnothing 6y ago
    In the US, natural gas averages $11.85 per 1,000 cubic feet. Electric averages $0.13 / kwh. 1,000 cubic feet of natural gas is a bit over 1 million BTU. That converts to 297 kwh of electricity. that 1,015,000 btu costs: $38.61 in electric $11.85 in natural gas
    - aidenn0 6y ago
      So 3-4x rather than 5-10x
- gregmac 6y ago
  > New buildings are rather efficient in US. They can be, and there's lots of modern construction techniques that are really good (search term "building science"). One big problem is that a lot of stuff is still built to "minimum code" which just isn't that great. On top of that, sloppy construction work can significantly undermine what is done. In my own house I've fixed several simple things, like missing insulation around vents and holes cut too big (or created by a hammer, rather than cutting). Here's a good walkthrough of a house under construction showing lots of problems typical to any subdivision (non-custom) build: https://youtu.be/OmU2N_Q732A https://youtu.be/OmU2N_Q732A
outworlder 6y ago
> What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air right back out into the environment. In the case of the house I'm currently at, it is pretty good at retaining heat in "winter" (in quotes, because it's Bay Area winter). However, in the summer it will be quite warm late at night. So sometimes I want it the other way around, I want it to radiate excess heat away as fast as possible, but I can't control that. We should be able to deploy "heatsinks" at night. That's for a house. Modern office buildings are built like greenhouses, even when they are otherwise insulated. We can't really roll out solar panels fast enough. They would help offsetting the cooling energy costs by a lot. After all, it's during warm sunny days where the air-conditioning needs are the greatest. They also provide shade.
dghughes 6y ago
Portable air conditioners are bad. All the hot components are in the room with you and it takes air from the room and blows it outside. Technology Connections has a good video about this: https://youtu.be/_-mBeYC2KGc?t=355 https://youtu.be/_-mBeYC2KGc?t=355
- userbinator 6y ago
  That's true of the ones that have only one hose to the outside. Those with two hoses are much better, especially if you insulate the hoses: https://news.ycombinator.com/item?id=24023979 https://news.ycombinator.com/item?id=24023979
  - thescriptkiddie 6y ago
    I was recently shopping for an AC unit and had to get a portable one because I have bars over my windows. Having seen the Technology Connections video I naturally tried to get a dual-hose model, but after seeing the specs (and the prices) I ended up getting a single-hose model anyway. If we go by the DOE SACC ratings, this single-hose toshiba [0] has a 14% higher SACC rating than this dual hose whynter [1], for the same BTU/hr rating. If we go by the wattage ratings (note: these are usually peak rather than average), the toshiba does use 13% more power than the whynter, so let's assume it cancels out and they both have the same energy efficiency. The toshiba is still $144 cheaper than the whynter. That's hard to justify for "dual hoses seem like they should be more efficient" without any actual evidence. Please prove me wrong, before it's too late for me to return the single-hose one. [0] https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/Portable-A-C/12,000-BTU---8,000-BTU-SACC-Portable-Air-Conditioner-with-Remote-Controller https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/P... [1] https://www.whynter.com/product/whynter-elite-12000-btu-dual-hose-digital-portable-air-conditioner/ https://www.whynter.com/product/whynter-elite-12000-btu-dual...
    - aeternum 6y ago
      The problem with an efficiency rating that includes air ingress is that the outdoor air temperature is an unconstrained variable. The dual hose unit will likely outperform significantly if the temperature delta is high, but if the temp delta is low then the single-hose unit is probably better as it likely has a more efficient compressor. It looks like DOE SACC tests assume the outdoor air temp is 83 degrees for 80% of your usage and 95 degrees for 20% of your usage.
ekianjo 6y ago
> The notoriously bad energy efficiency of air conditioners Their efficiency is based on thermodynamics, so there's not much you can do to break the physical barriers.
- contravariant 6y ago
  I'm fairly certain air conditioners aren't operating anywhere near the thermodynamic limit. At ordinary ambient temperature you could maintain a temperature difference of 10C with about 3000% efficiency.

ianai 6y ago

There’s also no obvious market factor incentivizing modernization of old RE let alone efficiency.

eggsnbacon1 6y ago

New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true. Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference. The misconception persists because heat uses gas, which is 5-10X less expensive per BTU of energy than electricity. So it might be cheaper to heat cold areas than run AC in hot ones, but its much more damaging to the environment. Plus, hot climates are using a lot of renewables these days which impacts the environmental friendliness of electric but not gas. I expect migration to the sun belt to accelerate, at least in the US. It makes a lot of sense from environmental perspectives. In some southern cities there's already long stretches every summer where daytime AC use runs on 70%+ renewable energy.

marcinzm 6y ago
[I was wrong]
- roywiggins 6y ago
  Air conditioners are often more than 100% efficient- they move more heat energy than they consume. (Of course if you start with a fossil fuel, turn it into electricity, and then pipe that into an AC unit, the overall efficiency will be dropped by the efficiency of the power plant, but it's still somewhat made up for by the advantages of heat pumps)
  - username505 6y ago
    This is false
    - URSpider94 6y ago
      What is false?
      - username505 6y ago
        The total efficiency of an air conditioner will never be more than 100% based on design; you will never be able to remove more heat than what the system produces in net cooling effect based off of the energy consumption created from compression - this is what would lead you to the eventual path of the theory of the heat death of the universe. You may be able to remove heat from one place to another but never more than what the system produces. Heating systems are completely different regarding efficiency.
        tripletao 6y ago
        The ratio of thermal power moved to electrical power input is more properly called "coefficient of performance" rather than "efficiency", but it's far greater than 100% in modern equipment. > From 1990 to 2013, U.S. shipment-weighted efficiency for residential split-system A/Cs increased from 9.5 SEER (~2.2 COP) to 14.9 SEER (~3.8 COP). https://www.energy.gov/sites/prod/files/2016/07/f33/The%20Future%20of%20AC%20Report%20-%20Full%20Report_0.pdf https://www.energy.gov/sites/prod/files/2016/07/f33/The%20Fu...
        URSpider94 6y ago
- stephen_g 6y ago
  But heat pump heating and cooling has coefficient of performance / energy efficiency ratios around 3-4 (or even higher than 5 for certain applications!), so you more than make back your efficiency loss there.
dylan604 6y ago
It is amazing how tight we can make buildings today. I had to learn a lot about HVAC on a remodeling job a few years ago. I had no idea that the drywall can be sealed so tight that when the HVAC system is running it can be next to impossible to open a door without a pressure release duct. Also saw how the HVAC system had vents to bring in air from outside with baffles controlled by the system. Can't remember exact purpose something about helping help control humidity as well as regulation to bring in "fresh" air to mix with the "stale" air in the building. So some parts of construction techniques and building materials have improved significantly. However, when comparing the framing lumber used today to what was used in the 60s, I'm shocked that new construction doesn't fall over the first time the wolf huffs and puffs.
- sparker72678 6y ago
  The outdoor fresh air intakes are typically via ERVs (Energy recovery ventilation systems). These systems bring in fresh air, filter it, and typically run it through a heat exchanger to minimize energy losses as the fresh air comes and and the stale air goes out. The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous if not cycled regularly.
  - londons_explore 6y ago
    2020: ”Poisonous stuff in our houses... Bad! Let's vent it to the environment!” 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.
    - adrianN 6y ago
      Luckily most organic compounds you find in indoor air aren't very stable.
    - cyberdrunk 6y ago
      > 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe. That's the case in much of the world already... I live in area where there's tons of smog in the colder months and consider installing a system for bringing in filtered air from the outside, so that I won't have to open windows for the 6+ months smog period.
CarbyAu 6y ago
Best marketing voice: "Why migrate to the sunbelt? Burn gas and wait for climate change to bring the warmth to you!" ...sigh. I really hope it doesn't go this way.
- samplatt 6y ago
  Already has, mate. There's no turning back, just a matter of damage mitigation, now.
- tobyhinloopen 6y ago
  It already has. There is a noticeable shift in temperatures here in the Netherlands. Hot days are getting hotter and much more frequent. Snow is getting rare. We had a yearly ice skating event that never happens anymore because there is no ice. Weeks of 30C weather are getting more common while not long ago, hotter than 25C was considered exceptional. It’s like daily temperatures are just shifted +5 degrees within 2 decades. It’s not just my gut feeling, there are plenty of statistics
  - the-dude 6y ago
    Which yearly event was this?
    - himlion 6y ago
      https://en.wikipedia.org/wiki/Elfstedentocht https://en.wikipedia.org/wiki/Elfstedentocht
      - the-dude 6y ago
        This event took place 15 times in the last century. How can this be yearly?
        himlion 6y ago
        I agree it's hardly a yearly event, but this is definitely the even he is referring to. Theoretically yearly would be a better term.
DoofusOfDeath 6y ago
> New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I was describing my home renovation project to someone who lives in Brazil. I don't how true this is for that entire country, but she said that it's very uncommon for Brazilian homes to have insulation.
- fyfy18 6y ago
  This is the same for many homes in Spain and Portugal too. For most of the year it's warm enough outside and you can be comfortable without AC (especially if you are in an older building with thick stone walls), but then for the one or two months of winter it is so cold inside, even though it may only get down to 10C (50F) outside. Most houses rely on resistive electric heaters (if they have any) which end up being very expensive to run. I live in a modern house in Northern Europe, and we don't even turn our heating on until it gets below freezing. Because we have good insulation, only then it starts to drop below 22C (72F) inside.
  - gallegojaime 6y ago
    Completely true, many old homes in Madrid are freezing in the winter. New homes are more regulated in efficiency, however. I lived in a new A-rated flat with sophisticated central heating and thermosolar, paying 500€/mo for the actual home and about 10€/mo for heating.
    - pmontra 6y ago
      Adding to this, I spent a week in a A-rated house. 30+ C outside and I never even looked for the remote of the air conditioner.
aidenn0 6y ago
Is NG really over 5X cheaper than electricity? It seems like a NG genset that is better than 20% efficient wouldn't be that hard to build, yet I don't see people running their houses off of electricity that way.
- kingnothing 6y ago
  In the US, natural gas averages $11.85 per 1,000 cubic feet. Electric averages $0.13 / kwh. 1,000 cubic feet of natural gas is a bit over 1 million BTU. That converts to 297 kwh of electricity. that 1,015,000 btu costs: $38.61 in electric $11.85 in natural gas
  - aidenn0 6y ago
    So 3-4x rather than 5-10x
gregmac 6y ago
> New buildings are rather efficient in US. They can be, and there's lots of modern construction techniques that are really good (search term "building science"). One big problem is that a lot of stuff is still built to "minimum code" which just isn't that great. On top of that, sloppy construction work can significantly undermine what is done. In my own house I've fixed several simple things, like missing insulation around vents and holes cut too big (or created by a hammer, rather than cutting). Here's a good walkthrough of a house under construction showing lots of problems typical to any subdivision (non-custom) build: https://youtu.be/OmU2N_Q732A https://youtu.be/OmU2N_Q732A

outworlder 6y ago

> What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air right back out into the environment. In the case of the house I'm currently at, it is pretty good at retaining heat in "winter" (in quotes, because it's Bay Area winter). However, in the summer it will be quite warm late at night. So sometimes I want it the other way around, I want it to radiate excess heat away as fast as possible, but I can't control that. We should be able to deploy "heatsinks" at night. That's for a house. Modern office buildings are built like greenhouses, even when they are otherwise insulated. We can't really roll out solar panels fast enough. They would help offsetting the cooling energy costs by a lot. After all, it's during warm sunny days where the air-conditioning needs are the greatest. They also provide shade.

dghughes 6y ago

Portable air conditioners are bad. All the hot components are in the room with you and it takes air from the room and blows it outside. Technology Connections has a good video about this: https://youtu.be/_-mBeYC2KGc?t=355 https://youtu.be/_-mBeYC2KGc?t=355

userbinator 6y ago
That's true of the ones that have only one hose to the outside. Those with two hoses are much better, especially if you insulate the hoses: https://news.ycombinator.com/item?id=24023979 https://news.ycombinator.com/item?id=24023979
- thescriptkiddie 6y ago
  I was recently shopping for an AC unit and had to get a portable one because I have bars over my windows. Having seen the Technology Connections video I naturally tried to get a dual-hose model, but after seeing the specs (and the prices) I ended up getting a single-hose model anyway. If we go by the DOE SACC ratings, this single-hose toshiba [0] has a 14% higher SACC rating than this dual hose whynter [1], for the same BTU/hr rating. If we go by the wattage ratings (note: these are usually peak rather than average), the toshiba does use 13% more power than the whynter, so let's assume it cancels out and they both have the same energy efficiency. The toshiba is still $144 cheaper than the whynter. That's hard to justify for "dual hoses seem like they should be more efficient" without any actual evidence. Please prove me wrong, before it's too late for me to return the single-hose one. [0] https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/Portable-A-C/12,000-BTU---8,000-BTU-SACC-Portable-Air-Conditioner-with-Remote-Controller https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/P... [1] https://www.whynter.com/product/whynter-elite-12000-btu-dual-hose-digital-portable-air-conditioner/ https://www.whynter.com/product/whynter-elite-12000-btu-dual...
  - aeternum 6y ago
    The problem with an efficiency rating that includes air ingress is that the outdoor air temperature is an unconstrained variable. The dual hose unit will likely outperform significantly if the temperature delta is high, but if the temp delta is low then the single-hose unit is probably better as it likely has a more efficient compressor. It looks like DOE SACC tests assume the outdoor air temp is 83 degrees for 80% of your usage and 95 degrees for 20% of your usage.

ekianjo 6y ago

> The notoriously bad energy efficiency of air conditioners Their efficiency is based on thermodynamics, so there's not much you can do to break the physical barriers.

contravariant 6y ago
I'm fairly certain air conditioners aren't operating anywhere near the thermodynamic limit. At ordinary ambient temperature you could maintain a temperature difference of 10C with about 3000% efficiency.