6 ms·

> The Lawrence Berkeley study argues that even a 30 percent improvement in efficiency could avoid the peak load equivalent of about 1,500 power plants by 2030.

> The Lawrence Berkeley study argues that even a 30 percent improvement in efficiency could avoid the peak load equivalent of about 1,500 power plants by 2030. Okay, but where is this 30% jump in efficiency going to come from? That seems like a pretty big leap!

klodolph 9y ago
Off the top of my head, * A lot of home conditioners are fighting the weather in conditions with poor insulation, running when nobody is home, or running in rooms when people are in different parts of the house. * Office air conditioners are often set too cold, subjectively speaking, sometimes resulting in workers bringing sweaters or even space heaters to their desks. This is shockingly common. Multi-zone cooling can make things more uniform, and if you can get people to stop using space heaters during the summer, that can make a big difference. Gender is supposedly a huge factor in temperature preferences, and offices are set to men's cooler preferences. In some locations this is exacerbated by the fact that men wear suits and ties while the women wear skirts and weather-appropriate tops. Personally, I want an air conditioner system that isn't set to a specific temperature, but instead reduces the extreme temperatures outside. So instead of keeping it set at 22 degrees, maybe it would be set to 22 degrees when it's 27 degrees out, but the AC goes to 25 degrees when it's 35 degrees out. I find this more comfortable, because there's less of a shock when going outside or coming inside.
- RcouF1uZ4gsC 9y ago
  The issue in cooling preferences is that if it is too cold, people can wear sweaters or even bring space heaters. If it is too hot, there is not much you can do. I think this problem is exacerbated by open office plans. If you have private/semi-private offices, you can probably do a much better job of controlling local temperature.
  - LeifCarrotson 9y ago
    We have private offices, but central HVAC. Multi-zone cooling (independent of having lots of little, less efficient window/through-wall units) is relatively uncommon. It's exacerbated (good word) by the fact that the large front office has mostly women sitting at low-power PCs, the offices are mostly men at powerful workstations (aka space heaters), and the HVAC ducts run though the office drop ceilings, meaning anyone doing physical projects in the central work space is the least cooled while our receptionist has been seen with a space heater.
    - grogenaut 9y ago
      doesn't that mean you use less power though?
    - cestith 9y ago
      Central HVAC can be zoned somewhat with thermocouple-adjustable or computer-controlled baffles. If you have a consistent over-cooling of one area and under-cooling of another there are magnetic strips made to partially cover the registers, or registers with adjustable baffles built in.
  - emodendroket 9y ago
    I'm not sure such a thing would work here, but Japan famously ran their "Cool Biz" campaign to encourage people to dress lighter in the summer. https://en.wikipedia.org/wiki/Cool_Biz_campaign https://en.wikipedia.org/wiki/Cool_Biz_campaign
    - grogenaut 9y ago
      I'm down with anything that gives me a reason to wear shorts and a tshirt at work!
    - Larrikin 9y ago
      The first company I worked at had cool biz tightly tied to time with zero regard to the actual temperature outside. It usually came too late and ended too early. Thankfully the next place I worked at was a lot more lax in the policy.
  - stardek 9y ago
    This is something being explored in a small trial here at the University of Waterloo. A lab has distributed several small fan/heaters that sense your presence and learn your temperature preferences then heat/cool just your local area. https://blizzard.cs.uwaterloo.ca/spotstar https://blizzard.cs.uwaterloo.ca/spotstar
- JumpCrisscross 9y ago
  > Gender is supposedly a huge factor in temperature preferences Source?
  - mperham 9y ago
    Every (hetero) marriage.
    - LeifCarrotson 9y ago
      This is one case where the plural of anecdote is, indeed, data. But I am grateful to see a sibling comment cite a proper study confirming what we already knew.
  - dangrossman 9y ago
    "In this study gender differences in thermal comfort and use of thermostats were examined by a quantitative interview survey with a total of 3094 respondents, and by controlled experiments. The studies were carried out in Finland and considered everyday thermal environments: homes, offices and a university. The results show significant gender differences in thermal comfort, temperature preference, and use of thermostats. Females are less satisfied with room temperatures than males, prefer higher room temperatures than males, and feel both uncomfortably cold and uncomfortably hot more often than males." "Gender differences in thermal comfort and use of thermostats in everyday thermal environments". Building and Environment, Volume 42, Issue 4, April 2007, Pages 1594-1603
  - Eric_WVGG 9y ago
    http://www.newyorker.com/tech/elements/is-your-thermostat-sexist http://www.newyorker.com/tech/elements/is-your-thermostat-se... The biological reasoning, as I understand it, is that men have a higher ratio of heat-generating muscle than women. When I first moved to NYC, I was bewildered by all the women walking around with scarves and summer dresses; it was explained to me that this was a strategy to optimize being comfortable in the outdoor heat, and then having something to withstand the frigid offices. (Personally, I'm of the opinion that one should acclimate to their climate, and folks who hate the heat wouldn't mind it so much if they didn't coddle themselves with AC all the time.)
- jrs235 9y ago
  All the more reason we need to find a way to make remote work work for positions and jobs that allow it. Most people are already heating and cooling their homes while away at the office. How much energy can we save and how much more comfortable can we be if we work from our homes? Additionally less energy is consumed and less pollution generated from not having to commute.
  - rplst8 9y ago
    Bingo! WFH = less traffic, less industrial building construction, less heating/cooling of empty spaces (offices at night, homes during day), less indoor lighting usage (homes are usually very well lit from outside light while most cubical jungles are lit by fluorescent lighting). Wanna save the environment? WFH!
  - khedoros1 9y ago
    The next move I do is definitely going to include the requirement of some kind of workspace for me and my wife. Right now, working from home means sitting on my bed with a laptop.
- Nition 9y ago
  Also, people who set their home heat pump to "auto" instead of "heat" in winter and "cool" in summer. No-one should mind if they have it on 18 in winter and the sun heats the room to 20 in the afternoon, but a heat pump on auto will start cooling to maintain the room at 18.
  - DiabloD3 9y ago
    I also agree, if you have a heat pump do not use auto mode, it will never do what you actually want.
    - rplst8 9y ago
      While it's not the best thing to do, it doesn't matter much as the efficiency of the systems go way way up when the outside temp is near the same as the inside temp.
  - wongarsu 9y ago
    I've never understood why we even design most HVAC systems to maintain one temperature. I don't care that my home or car is exactly 18°C warm, I just want to keep it at a temperature between 18°C and 25°C year-round. It feels completely unnatural to be forced to set a single temperature and change it depending on the situation. A less straightforward change for further automation would be to make that temperature depending on the humidity. On a dry day, 28°C is perfectly fine, on a humid day it's way too hot. I can't be bothered to adjust my desired temperature depending on humidity, but a computer could easily do that.
    - Nition 9y ago
      Hell yes, let me set a min and a max! Although to be honest where I live, we wouldn't need it. We never really need to heat and cool on the same day.
  - cestith 9y ago
    My system has separate "heat if below" and "cool if above" settings for its program, variable by user-defined portions of the day and by the (pre-set of course) days of the week.
- mannykannot 9y ago
  Ceiling fans reduce the need for AC, especially overnight - even gentle circulation makes a noticeable difference. Also, an attic fan that can blow cool overnight air through the building whenever the temperature and humidity outside are acceptably low might reduce the expenditure of AC on cooling down the structure. A small degree of automation would allow these measures to work together with the AC.
  - curun1r 9y ago
    I spent much of last year traveling around Southeast Asia and I always opted for fan rooms over A/C whenever possible. Yes, they were warmer, but once you got used to it, it wasn't a problem. But the best part about it was the lack of the respiratory problems that went along with A/C. In humid environments like the tropics, going between wet air and dry air can be really rough on the sinuses. I wonder how many people have respiratory problems that they chalk up to allergies and whatnot that are actually due to the breathing overly-dry A/C air.
- microcolonel 9y ago
  In addition to men preferring cooler temperatures in general (probably for metabolic reasons), men in offices are usually required to wear warmer clothing than women (though anecdotally I suspect that because of the AC, pantsuits are becoming more popular). In one office I worked at, the AC controls were not accessible, and because there was no dress code whatsoever, everyone complained about the temperatures being too low. There was a TI office in the same building, and because everyone was in business casual or higher, they didn't have the same problems. Designing uniforms which look professional and composed but which also ventilate correctly could considerably raise optimal office temperatures.
  - grogenaut 9y ago
    "Looks professional" is all about what "successful people" wear. If everyone in the US who was successful took to wearing Moomoos... then we'd all be wearing moomoos and the schlubs would be wearing suits. Just look at the hoodie pre and post zuckerberg. If Mark had instead wore a tank-top and board shorts 50% of SF would be wearing that year round instead.
    - microcolonel 9y ago
      No, there really is something objectively attractive about handsome clothing. Well made and handsome clothing, especially that which obscures the aesthetic weaknesses of the wearer, is a global concept. Hoodie and jeans is an okay uniform inside a business (though I would argue that if they're not well-kept, it lowers the standards of the people in the office), but in customer-facing roles I think it's inappropriate. It can be done well, but most hoodies and most pairs of jeans are an aesthetic disappointment, since they're built for casual warmth and gold panning respectively. I would not trust a bank which faces its customers with hoodies, T-shirts, and jeans. The appropriate attire for a clerk usually involves a shirt (especially with a vest) or one/two tone blouse, and trousers or a skirt. Makes you look kempt, but dynamic. A unifying visual theme for staff also makes it simpler to identify them. If the clerks all have a consistent uniform, the custodial staff a different but thematically matched uniform, it makes it simpler to navigate a customer-facing office. I think Hooters does a good job of this, it is easy to locate and discern the staff from other guests, and contributes to the environment (a casual, consistent dining establishment which has attractive, well-trained, and helpful service staff).
- 21 9y ago
  A lot of offices don't even bother to turn the AC, or the lights off at night. A lot of people just leave their computers on (with sleep disabled), just because they don't want to wait 30 sec for the boot or to start their apps.
  - grogenaut 9y ago
    I leave my pc on because if there is an issue I need to be able to remote into it and there's no "wake on lan" type enterprise thing setup (don't even know if that exists). I could drive in but the gas cost and time costs of that are higher (my guess) than leaving the pc in idle 24/7.
guelo 9y ago
It's already available. In the USA there's a efficiency rating called SEER which the federal government mandates new ACs must be at least rated at SEER 13. But if you want to spend the money you can buy ACs with SEER ratings above 25.
chiph 9y ago
Most home AC units in the US are single-stage, where they're all the way on, or all the way off. You can pay more for a two-stage unit, which has low & high operation. But in other countries, VRF systems are more popular (variable refrigerant flow) - they operate their fans & compressors at speeds which match the demand, and so use less electricity. And are quieter.
- sureshv 9y ago
  There's also a cost issue: If you have a one stage furnace - your only option is a one stage AC (vs 2-stage or variable speed AC). You need to upgrade the furnace/blower to take advantage of the more efficient AC model Mini-Splits are great but much more expensive to purchase (~4k USD per Unit which covers 400-500 sqft). They also don't heat as well as a traditional gas fired furnace. Heat pumps are probably the way to go in moderate climates but I haven't looked into them in much detail.
thebooktocome 9y ago
Some of it can come from social engineering instead of HVAC technical breakthroughs -- automated thermostats like the Nest, hand-held body-coolers like http://news.mit.edu/2013/madmec-design-competition-1017 http://news.mit.edu/2013/madmec-design-competition-1017 Better summer clothes will help too. I've been pretty impressed by advances in cooling undergarments that are designed to wick away moisture and encourage air flow. Anyway, all of these seemingly unrelated things contribute to improved AC efficiency.
Scramblejams 9y ago
It's been mentioned elsewhere in this thread, but if you run your refrigerant loop through the ground instead of cooling it using the hot ambient air, you can absolutely achieve that improvement in efficiency. The concept is described here: https://energy.gov/energysaver/geothermal-heat-pumps https://energy.gov/energysaver/geothermal-heat-pumps The amount of efficiency increase you get depends on the ground temp, which varies by latitude, but I've seen 70% reductions in electricity usage quoted for systems installed in North America. A side benefit is you no longer have a big, loud heat exchanger running on the side or top of your house. The pump unit for a ground loop can sit inside your garage, it's about the size of two mini-fridges and only emits a quiet hum. Sidenote: When I bring up ground loop air conditioning in conversation with people, no one has ever heard of it. The technology has a marketing problem. That makes sense in states where electricity is cheap, but in places like California I'm surprised the state hasn't mandated them for new installations and offered tax breaks to give it some momentum.
- rplst8 9y ago
  The challenge for these is the cost. First, you either have to drill wells that are ~500 feet deep or lay coils of tubing under your yard (if you have one) below the frost line. Doing either is expensive, though the wells are much more so. The downside of the cheaper option (the coils under yard) is that earth shifts, and the coils will too. I've had two separate friends install these (usually 4-6 separate coils) only to have the earth move and rip open a coil or kink it. Usually you have a valve for each one to shut it off so the unit can sill operate on the remaining working coils, however with each lost coil the efficiency goes down. Also, the ground-source heat-pumps aren't cheap. They are in the $7-10k range - just for the unit - and not many people know how to repair them as they are a bit of a specialty item in the HVAC industry.
  - DannyBee 9y ago
    Sure, it's cost, but that's solvable. 1. Drilling the wells is not actually that expensive depending where you are. For me, 3 300 ft wells, bored, piped, and grouted, was about 5k. 2. The units can be gotten for that price with install. You need to take into account the fact that they are significantly more efficient at both heating, and cooling, and hot water, over their lifetime. (also, their specs and submittal data usually have real numbers, giving you mappings from incoming water temperature/etc to EER, not BS numbers like most outdoor air A/C units) They would also be cheaper if they sold more of them :) 3. The units are much easier to keep working, and pretty much never die. They are made much better than the average heat pump. As for your coils, yeah, doing horizontal loops is not a good plan in most cases, though cheaper. With the 30% federal tax credit that used to exist, a state tax credit, etc, i paid 10k all told. I made that back in 2 years (the electric bill in the winter went from 600 a month to 100. Yes, the heat pump was functioning properly) In areas of the country where well drilling is more common, it's a great option. I wouldn't do it in say, the bay area. But note: none of the wells have to be that expensive to drill, and in fact, when done during new construction, they are often really cheap. It's just a matter of, in various parts of the country, limited set of people have well drilling rigs because it's not that common. So part of the cost may be "having some guys drive a well drilling rig 5-6 hours to come handle it"
sandover 9y ago
If you're in the US, you can likely save much more than 30% today by replacing a central air system with a ductless mini-split style system. These are already dominant in the rest of the world, however.
- RcouF1uZ4gsC 9y ago
  I actually saw an installation in a new apartment. After seeing that, I much preferred central AC. One of the nice things about the US style central AC systems, is that the bathrooms are comfortable. In the split style system, a few rooms (bedrooms/living room) may be comfortable but other rooms (such as bathrooms) are miserably stuffy.
- neuronexmachina 9y ago
  What makes them so much more efficient?
  - 21 9y ago
    Not a specialist, maybe less loss due to shorter distances.
mtgentry 9y ago
I spoke with an HVAC guy over the weekend about just this topic. He said about 4 yrs ago, the state of CA required all new construction to have ducting that goes to and from, each room in a house. So when Jr. goes off to college, you can close the door and not send cool air to his room. I think he said it's something like 30% more efficient? But don't quote me on that.
rplst8 9y ago
Well, the efficiency of a heat pump/refrigerator is limited by Carnot's theorem. Essentially it boils down to the difference of the outside temperature compared to inside temperature. With an indoor temp of ~72F and outdoor ~90F the maximum efficiency is a COP of about 30. Current AC units are in the 2 to 4 range. So a 30% increase doesn't seem impossible that low on the efficiency scale. There was a recent similar jump in efficiency when the US raised the minimum SEER standards for new systems from 10 to 13.

klodolph 9y ago

Off the top of my head, * A lot of home conditioners are fighting the weather in conditions with poor insulation, running when nobody is home, or running in rooms when people are in different parts of the house. * Office air conditioners are often set too cold, subjectively speaking, sometimes resulting in workers bringing sweaters or even space heaters to their desks. This is shockingly common. Multi-zone cooling can make things more uniform, and if you can get people to stop using space heaters during the summer, that can make a big difference. Gender is supposedly a huge factor in temperature preferences, and offices are set to men's cooler preferences. In some locations this is exacerbated by the fact that men wear suits and ties while the women wear skirts and weather-appropriate tops. Personally, I want an air conditioner system that isn't set to a specific temperature, but instead reduces the extreme temperatures outside. So instead of keeping it set at 22 degrees, maybe it would be set to 22 degrees when it's 27 degrees out, but the AC goes to 25 degrees when it's 35 degrees out. I find this more comfortable, because there's less of a shock when going outside or coming inside.

RcouF1uZ4gsC 9y ago
The issue in cooling preferences is that if it is too cold, people can wear sweaters or even bring space heaters. If it is too hot, there is not much you can do. I think this problem is exacerbated by open office plans. If you have private/semi-private offices, you can probably do a much better job of controlling local temperature.
- LeifCarrotson 9y ago
  We have private offices, but central HVAC. Multi-zone cooling (independent of having lots of little, less efficient window/through-wall units) is relatively uncommon. It's exacerbated (good word) by the fact that the large front office has mostly women sitting at low-power PCs, the offices are mostly men at powerful workstations (aka space heaters), and the HVAC ducts run though the office drop ceilings, meaning anyone doing physical projects in the central work space is the least cooled while our receptionist has been seen with a space heater.
  - grogenaut 9y ago
    doesn't that mean you use less power though?
  - cestith 9y ago
    Central HVAC can be zoned somewhat with thermocouple-adjustable or computer-controlled baffles. If you have a consistent over-cooling of one area and under-cooling of another there are magnetic strips made to partially cover the registers, or registers with adjustable baffles built in.
- emodendroket 9y ago
  I'm not sure such a thing would work here, but Japan famously ran their "Cool Biz" campaign to encourage people to dress lighter in the summer. https://en.wikipedia.org/wiki/Cool_Biz_campaign https://en.wikipedia.org/wiki/Cool_Biz_campaign
  - grogenaut 9y ago
    I'm down with anything that gives me a reason to wear shorts and a tshirt at work!
  - Larrikin 9y ago
    The first company I worked at had cool biz tightly tied to time with zero regard to the actual temperature outside. It usually came too late and ended too early. Thankfully the next place I worked at was a lot more lax in the policy.
- stardek 9y ago
  This is something being explored in a small trial here at the University of Waterloo. A lab has distributed several small fan/heaters that sense your presence and learn your temperature preferences then heat/cool just your local area. https://blizzard.cs.uwaterloo.ca/spotstar https://blizzard.cs.uwaterloo.ca/spotstar
JumpCrisscross 9y ago
> Gender is supposedly a huge factor in temperature preferences Source?
- mperham 9y ago
  Every (hetero) marriage.
  - LeifCarrotson 9y ago
    This is one case where the plural of anecdote is, indeed, data. But I am grateful to see a sibling comment cite a proper study confirming what we already knew.
- dangrossman 9y ago
  "In this study gender differences in thermal comfort and use of thermostats were examined by a quantitative interview survey with a total of 3094 respondents, and by controlled experiments. The studies were carried out in Finland and considered everyday thermal environments: homes, offices and a university. The results show significant gender differences in thermal comfort, temperature preference, and use of thermostats. Females are less satisfied with room temperatures than males, prefer higher room temperatures than males, and feel both uncomfortably cold and uncomfortably hot more often than males." "Gender differences in thermal comfort and use of thermostats in everyday thermal environments". Building and Environment, Volume 42, Issue 4, April 2007, Pages 1594-1603
- Eric_WVGG 9y ago
  http://www.newyorker.com/tech/elements/is-your-thermostat-sexist http://www.newyorker.com/tech/elements/is-your-thermostat-se... The biological reasoning, as I understand it, is that men have a higher ratio of heat-generating muscle than women. When I first moved to NYC, I was bewildered by all the women walking around with scarves and summer dresses; it was explained to me that this was a strategy to optimize being comfortable in the outdoor heat, and then having something to withstand the frigid offices. (Personally, I'm of the opinion that one should acclimate to their climate, and folks who hate the heat wouldn't mind it so much if they didn't coddle themselves with AC all the time.)
jrs235 9y ago
All the more reason we need to find a way to make remote work work for positions and jobs that allow it. Most people are already heating and cooling their homes while away at the office. How much energy can we save and how much more comfortable can we be if we work from our homes? Additionally less energy is consumed and less pollution generated from not having to commute.
- rplst8 9y ago
  Bingo! WFH = less traffic, less industrial building construction, less heating/cooling of empty spaces (offices at night, homes during day), less indoor lighting usage (homes are usually very well lit from outside light while most cubical jungles are lit by fluorescent lighting). Wanna save the environment? WFH!
- khedoros1 9y ago
  The next move I do is definitely going to include the requirement of some kind of workspace for me and my wife. Right now, working from home means sitting on my bed with a laptop.
Nition 9y ago
Also, people who set their home heat pump to "auto" instead of "heat" in winter and "cool" in summer. No-one should mind if they have it on 18 in winter and the sun heats the room to 20 in the afternoon, but a heat pump on auto will start cooling to maintain the room at 18.
- DiabloD3 9y ago
  I also agree, if you have a heat pump do not use auto mode, it will never do what you actually want.
  - rplst8 9y ago
    While it's not the best thing to do, it doesn't matter much as the efficiency of the systems go way way up when the outside temp is near the same as the inside temp.
- wongarsu 9y ago
  I've never understood why we even design most HVAC systems to maintain one temperature. I don't care that my home or car is exactly 18°C warm, I just want to keep it at a temperature between 18°C and 25°C year-round. It feels completely unnatural to be forced to set a single temperature and change it depending on the situation. A less straightforward change for further automation would be to make that temperature depending on the humidity. On a dry day, 28°C is perfectly fine, on a humid day it's way too hot. I can't be bothered to adjust my desired temperature depending on humidity, but a computer could easily do that.
  - Nition 9y ago
    Hell yes, let me set a min and a max! Although to be honest where I live, we wouldn't need it. We never really need to heat and cool on the same day.
- cestith 9y ago
  My system has separate "heat if below" and "cool if above" settings for its program, variable by user-defined portions of the day and by the (pre-set of course) days of the week.
mannykannot 9y ago
Ceiling fans reduce the need for AC, especially overnight - even gentle circulation makes a noticeable difference. Also, an attic fan that can blow cool overnight air through the building whenever the temperature and humidity outside are acceptably low might reduce the expenditure of AC on cooling down the structure. A small degree of automation would allow these measures to work together with the AC.
- curun1r 9y ago
  I spent much of last year traveling around Southeast Asia and I always opted for fan rooms over A/C whenever possible. Yes, they were warmer, but once you got used to it, it wasn't a problem. But the best part about it was the lack of the respiratory problems that went along with A/C. In humid environments like the tropics, going between wet air and dry air can be really rough on the sinuses. I wonder how many people have respiratory problems that they chalk up to allergies and whatnot that are actually due to the breathing overly-dry A/C air.
microcolonel 9y ago
In addition to men preferring cooler temperatures in general (probably for metabolic reasons), men in offices are usually required to wear warmer clothing than women (though anecdotally I suspect that because of the AC, pantsuits are becoming more popular). In one office I worked at, the AC controls were not accessible, and because there was no dress code whatsoever, everyone complained about the temperatures being too low. There was a TI office in the same building, and because everyone was in business casual or higher, they didn't have the same problems. Designing uniforms which look professional and composed but which also ventilate correctly could considerably raise optimal office temperatures.
- grogenaut 9y ago
  "Looks professional" is all about what "successful people" wear. If everyone in the US who was successful took to wearing Moomoos... then we'd all be wearing moomoos and the schlubs would be wearing suits. Just look at the hoodie pre and post zuckerberg. If Mark had instead wore a tank-top and board shorts 50% of SF would be wearing that year round instead.
  - microcolonel 9y ago
    No, there really is something objectively attractive about handsome clothing. Well made and handsome clothing, especially that which obscures the aesthetic weaknesses of the wearer, is a global concept. Hoodie and jeans is an okay uniform inside a business (though I would argue that if they're not well-kept, it lowers the standards of the people in the office), but in customer-facing roles I think it's inappropriate. It can be done well, but most hoodies and most pairs of jeans are an aesthetic disappointment, since they're built for casual warmth and gold panning respectively. I would not trust a bank which faces its customers with hoodies, T-shirts, and jeans. The appropriate attire for a clerk usually involves a shirt (especially with a vest) or one/two tone blouse, and trousers or a skirt. Makes you look kempt, but dynamic. A unifying visual theme for staff also makes it simpler to identify them. If the clerks all have a consistent uniform, the custodial staff a different but thematically matched uniform, it makes it simpler to navigate a customer-facing office. I think Hooters does a good job of this, it is easy to locate and discern the staff from other guests, and contributes to the environment (a casual, consistent dining establishment which has attractive, well-trained, and helpful service staff).
21 9y ago
A lot of offices don't even bother to turn the AC, or the lights off at night. A lot of people just leave their computers on (with sleep disabled), just because they don't want to wait 30 sec for the boot or to start their apps.
- grogenaut 9y ago
  I leave my pc on because if there is an issue I need to be able to remote into it and there's no "wake on lan" type enterprise thing setup (don't even know if that exists). I could drive in but the gas cost and time costs of that are higher (my guess) than leaving the pc in idle 24/7.

guelo 9y ago

It's already available. In the USA there's a efficiency rating called SEER which the federal government mandates new ACs must be at least rated at SEER 13. But if you want to spend the money you can buy ACs with SEER ratings above 25.

chiph 9y ago

Most home AC units in the US are single-stage, where they're all the way on, or all the way off. You can pay more for a two-stage unit, which has low & high operation. But in other countries, VRF systems are more popular (variable refrigerant flow) - they operate their fans & compressors at speeds which match the demand, and so use less electricity. And are quieter.

sureshv 9y ago
There's also a cost issue: If you have a one stage furnace - your only option is a one stage AC (vs 2-stage or variable speed AC). You need to upgrade the furnace/blower to take advantage of the more efficient AC model Mini-Splits are great but much more expensive to purchase (~4k USD per Unit which covers 400-500 sqft). They also don't heat as well as a traditional gas fired furnace. Heat pumps are probably the way to go in moderate climates but I haven't looked into them in much detail.

thebooktocome 9y ago

Some of it can come from social engineering instead of HVAC technical breakthroughs -- automated thermostats like the Nest, hand-held body-coolers like http://news.mit.edu/2013/madmec-design-competition-1017 http://news.mit.edu/2013/madmec-design-competition-1017 Better summer clothes will help too. I've been pretty impressed by advances in cooling undergarments that are designed to wick away moisture and encourage air flow. Anyway, all of these seemingly unrelated things contribute to improved AC efficiency.

Scramblejams 9y ago

It's been mentioned elsewhere in this thread, but if you run your refrigerant loop through the ground instead of cooling it using the hot ambient air, you can absolutely achieve that improvement in efficiency. The concept is described here: https://energy.gov/energysaver/geothermal-heat-pumps https://energy.gov/energysaver/geothermal-heat-pumps The amount of efficiency increase you get depends on the ground temp, which varies by latitude, but I've seen 70% reductions in electricity usage quoted for systems installed in North America. A side benefit is you no longer have a big, loud heat exchanger running on the side or top of your house. The pump unit for a ground loop can sit inside your garage, it's about the size of two mini-fridges and only emits a quiet hum. Sidenote: When I bring up ground loop air conditioning in conversation with people, no one has ever heard of it. The technology has a marketing problem. That makes sense in states where electricity is cheap, but in places like California I'm surprised the state hasn't mandated them for new installations and offered tax breaks to give it some momentum.

rplst8 9y ago
The challenge for these is the cost. First, you either have to drill wells that are ~500 feet deep or lay coils of tubing under your yard (if you have one) below the frost line. Doing either is expensive, though the wells are much more so. The downside of the cheaper option (the coils under yard) is that earth shifts, and the coils will too. I've had two separate friends install these (usually 4-6 separate coils) only to have the earth move and rip open a coil or kink it. Usually you have a valve for each one to shut it off so the unit can sill operate on the remaining working coils, however with each lost coil the efficiency goes down. Also, the ground-source heat-pumps aren't cheap. They are in the $7-10k range - just for the unit - and not many people know how to repair them as they are a bit of a specialty item in the HVAC industry.
- DannyBee 9y ago
  Sure, it's cost, but that's solvable. 1. Drilling the wells is not actually that expensive depending where you are. For me, 3 300 ft wells, bored, piped, and grouted, was about 5k. 2. The units can be gotten for that price with install. You need to take into account the fact that they are significantly more efficient at both heating, and cooling, and hot water, over their lifetime. (also, their specs and submittal data usually have real numbers, giving you mappings from incoming water temperature/etc to EER, not BS numbers like most outdoor air A/C units) They would also be cheaper if they sold more of them :) 3. The units are much easier to keep working, and pretty much never die. They are made much better than the average heat pump. As for your coils, yeah, doing horizontal loops is not a good plan in most cases, though cheaper. With the 30% federal tax credit that used to exist, a state tax credit, etc, i paid 10k all told. I made that back in 2 years (the electric bill in the winter went from 600 a month to 100. Yes, the heat pump was functioning properly) In areas of the country where well drilling is more common, it's a great option. I wouldn't do it in say, the bay area. But note: none of the wells have to be that expensive to drill, and in fact, when done during new construction, they are often really cheap. It's just a matter of, in various parts of the country, limited set of people have well drilling rigs because it's not that common. So part of the cost may be "having some guys drive a well drilling rig 5-6 hours to come handle it"

sandover 9y ago

If you're in the US, you can likely save much more than 30% today by replacing a central air system with a ductless mini-split style system. These are already dominant in the rest of the world, however.

RcouF1uZ4gsC 9y ago
I actually saw an installation in a new apartment. After seeing that, I much preferred central AC. One of the nice things about the US style central AC systems, is that the bathrooms are comfortable. In the split style system, a few rooms (bedrooms/living room) may be comfortable but other rooms (such as bathrooms) are miserably stuffy.
neuronexmachina 9y ago
What makes them so much more efficient?
- 21 9y ago
  Not a specialist, maybe less loss due to shorter distances.

mtgentry 9y ago

I spoke with an HVAC guy over the weekend about just this topic. He said about 4 yrs ago, the state of CA required all new construction to have ducting that goes to and from, each room in a house. So when Jr. goes off to college, you can close the door and not send cool air to his room. I think he said it's something like 30% more efficient? But don't quote me on that.

rplst8 9y ago

Well, the efficiency of a heat pump/refrigerator is limited by Carnot's theorem. Essentially it boils down to the difference of the outside temperature compared to inside temperature. With an indoor temp of ~72F and outdoor ~90F the maximum efficiency is a COP of about 30. Current AC units are in the 2 to 4 range. So a 30% increase doesn't seem impossible that low on the efficiency scale. There was a recent similar jump in efficiency when the US raised the minimum SEER standards for new systems from 10 to 13.