Dear Umbra,
I'm a girl trying to make it in a big, hot, airless city -- New York, that is. We're in the middle of a heat wave that will soon end, but the longer heat wave we call summer will continue, so I wonder: when the interior of my apartment is up to 93 degrees and I have no less than three fans oscillating, am I using more energy than I would if I purchased and used one energy-efficient air conditioner? What's the best choice here?
Elizabeth Q.
New York, N.Y.
Dearest Elizabeth,
I was in New York during that heat wave. My resultant suggestion is to carry a pail of ice water around the house with you, putting your feet into the pail each time you sit down. And don't visit the sea lions at the zoo, as you will be overcome with jealousy watching them swim about in their clear blue pool.
As far as your fans go, they probably consume less electricity than a very efficient window air conditioner, and they certainly consume less energy than an older model. It's hard to be exact without examining your very own fans, which should be marked somewhere with the maximum watts used. The DOE thinks a typical fan might draw 55 to 250 watts, which is a huge range; various other sources put the number at 87, 115, 150, and 200. Let us say three fans pull 450 watts -- and at most, using DOE's highest number, 750 watts.
Figuring the wattage of a window air conditioner is a bit more complex, but it likely is up near 1,000 watts for a typical unit. The size of an AC unit is usually measured in British Thermal Units, and the conditioner itself might be 6,000 BTUs or 18,000 BTUs; no one seems to care about the watts. Instead we need to care about the Energy Efficiency Rating, which is the ratio of cooling capacity to wattage (that is, the BTU divided by the watts). If we know the EER and the BTU, we can do a little math to figure the wattage (I'm sampling Energy Star-qualified units here, so they'll be low-watt). A unit with 8,050 BTU capacity and an EER of 10.8 draws 745 watts; one with the same EER but 10,000 BTUs draws 923 watts.
That's too many numbers, but here's the upshot: if the fans are keeping you cool enough, stay with the status quo, because they are either equal to or better than a high-efficiency room air conditioner. Air conditioners also may contain environmentally damaging refrigerants, and while these should not be difficult to contain and properly dispose, it still would be better to avoid using them.
If your current fans are not doing the job, consider installing (or asking your landlord to install) a ceiling fan, which uses even less power than a floor fan and can help the whole room feel cooler. Still not cool enough? If you need to purchase a window air conditioner, please size it correctly for your home and buy the most efficient unit you can afford. Energy Star lists qualified units, the Consortium for Energy Efficiency pushes "super-efficient" units, and the EERE gives installation and operation tips.
Either way, don't forget that neither fans nor AC should be operating when you are not at home. Fans make us feel cooler by convecting hot air away from our bods. If our bods are not there, the fan's energy is wasted. And though we may think leaving AC on all day is more energy-efficient than having it kick into action after we get home, it is not. I repeat: Leaving AC on all day is not energy-efficient. If you can't stand coming home to a hot house, get a timer for the AC and set it for half an hour before homecoming.
To get the most out of your fans, position them to grab at any slightly cooler air and push it past your bod. If the air outdoors is only going to make life hotter, close all the windows and shades until temperatures fall, and work with the air already in the house. Best of luck this summer.
Glowingly,
Umbra
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Comments
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Tsalco Posted 2:47 am
07 Jul 2008
That is simply not true in many instances. A fan may be bringing in cooler air from another location such as a basement or cool evening air and needs to run during all the cool hours to work effectively.
In my case, I use a strategically place double window-mount fan that use 50-75 watts. If used well in an area that cools off below indoor temperature at night it can cool off 1000 sq ft on low power for most nights. We live in a dry area where the summer days are often 80-95 degrees and the nights are 60-75 degrees.
The key is to place it at the coolest and lowest end of the structure and open the highest windows at the opposite end. Keep windows near the fan closed. It will push cool air through the entire place. We can cool our house off by about 10 degrees F on most days.
Keep ALL windows completely closed when the temp outside is hotter than inside. The instant the outside temp drops below the inside temp, open the windows and turn the fan on and LEAVE it on until the temps reverse again.
So, 50-75 watts with a fan on for less than 12 hours a day vs. 1000 watts for AC and there ain't no contest. The fan is the clear winner.
Our electric bill right now for a 2 person 2,000 sq ft house with a highly computerized office that is used all day is about $30-40/month in the summer.
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Ben Rosenthal Posted 3:13 am
07 Jul 2008
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BlueHorizon Posted 3:18 am
07 Jul 2008
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KenGreen Posted 5:01 am
07 Jul 2008
I've got one that I wear when I take the metro into the office here in D.C., and I can tell you, wearing one of these wraps under the collar of your shirt makes a huge difference. It also helps me keep cool at home when our AC isn't quite up to the task of offsetting the summer heat, or when I'm working out. Putting one on and then having your fan blow air past it will cool you down enormously. I believe other companies make caps that do the same thing.
(I have no stake in any producer of these things, just sharing a tip I use to keep my cool!)
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mearph Posted 5:23 am
07 Jul 2008
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shoreranger Posted 6:24 am
07 Jul 2008
Anyway, leaving your fan on all day is not going to effectively alleviate this problem.
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cmurthi Posted 7:27 am
07 Jul 2008
Quoting the DOE to get wattage of fans? And that extreme range...a 250w fan is like those giant 48" industrial air movers you see in factories. A table fan may be 50w.
Then the incorrect "no one seems to care about watts (on a/cs)" What? Every a/c ad. and certainly the a/c nameplate shows wattage used. Iae, the computation of watts=btu/eer is something even my 9 year could do, it's hardly "too many numbers."
Also, who uses 3 (250w!!) fans in a room to replace one a/c as noted in the comparison? The comparison of energy used should be 50-90w (fan) to 700-900w (a/c.)
Obviously, the a/c provides different comfort (not least the reduction of humidity which is in most cases more important than temp,) not mentioned by her.
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WaterConsNYC Posted 11:00 am
07 Jul 2008
As for the person with dogs, you may not like this answer but they might be happiest with a little kiddie pool that they can plop in.
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rlotz Posted 12:31 pm
07 Jul 2008
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TheAnalyst Posted 10:41 pm
07 Jul 2008
Umbra faild to discuss programmable AC units. On days mentioned above I need my AC especially after gardening outside and to relieve my allergies (or I could suffer with a constant headache from the humidity). When the AC is on, I always have it programmed to control itself at the highest temperature I can comfortably stand.
For someone who mentioned fans to be used to bring cool air from a basement, I'm sorry to say but that is impossible. Heat rises, and as my bedroom is on the second floor I can tell you there is no cool air moving up my stairs.
As far as the pets, if it is hot and you are uncomfortable, I'm sure they are since they are most likely covered in fur. I too keep the air on for my pets on very hot days (and it is programmed).
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KenGreen Posted 6:56 am
08 Jul 2008
It is astonishing that people ostensibly concerned about global warming, and who are willing to force others to change their lifestyles with regard to cars, housing, clothing, flying, and even limiting the number of children people can have feel free to own animals that have extensive carbon footprints due to their protein diets, energy used in heating and cooling, and the zillion-dollar pet products industry.
If environmentalists were honest, they'd tell you straight up that the great green future is one of no pet-ownership. But they won't admit that, since it would lose a significant fraction of their support from animal lovers who also love their pets.
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Gravelbabe Posted 8:29 am
08 Jul 2008
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rivergal Posted 9:17 am
08 Jul 2008
As for bringing cooler air up from the basement: I used to do this all the time when I lived in un-airconditioned older houses in eastern MA. Most basements in such houses have at least one window that opens, or a walkout door. If you open that window or door in the evening, open the door to the basement, and put a strong window fan in an upstairs window, directing the air OUT of the room (i.e. on the exhaust setting), you will feel cool air flooding your house from the ground floor up. Even in dwellings without basements a window fan set in the upper part of a double hung window can help bring cool evening air in while exhausting hot interior air. While cold air is denser than warm and will not rise without help, a fan can easily overcome this density differential.
No, this won't work in dense urban areas where nighttime temps never drop below 80.
Just don't do what a former roommate of mine insisted on doing: opening her bedroom windows wide all day to the hot outside air while leaving a powerful room fan on while she was out at work. No surprise that her room was at least 10 degrees hotter than the rest of the house by 5 PM . . .
All other thing being equal, a large, high ceilinged room, or a shady porch, will feel cooler than a small low room at the same temperature because our bodies actually absorb long wave radiation coming off solid objects like walls and ceilings. It's time we started designing buildings with some thought about climate and comfort. Time to bring back the screened porch for summer sleeping and after dinner living!
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John former Marine Posted 10:00 pm
08 Jul 2008
When it comes to cooling a house/apartment for the sake of the animals, don't bother. Unless it gets incredibly hot in there, you're just being wasteful. I'd say that as long as you leave water out for them every day, they'll be fine. I mean...it's not like they're running around and working hard when you're not home...they're just sitting in a window or sleeping. If it gets to 90 degrees, they may pant a bit but they'll be fine.
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TheAnalyst Posted 11:02 pm
08 Jul 2008
But as some have stated, pets take up energy. Is it a burden you are willing to deal with? If no, then don't have a pet.
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Delay And Deny Posted 11:40 pm
08 Jul 2008
If you gave up the apartment and moved to the suburbs you could hang out in your backyard, or sprawl in a hammock.
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Anad Posted 1:03 pm
09 Jul 2008
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leysha Posted 1:01 pm
10 Jul 2008
All environmentalists make some concessions, (just being alive is a big one). Some of us own pets because they give us companionship and fill emotional gaps in our lives. Others turn on the AC in the summer rather than use fans to be comfortable. The point is there are no perfect environmentalists, we all have non-green things we do for our health or sanity, and no activity is completely exempt from some sort of environmental impact. Everyone posting or reading these comments is using computer that is consuming electricity. We could all save power by shutting our computers off right now and never turning them on again, but for one reason or another we've decided that the benefits to ourselves of using a computer outweighs the environmental costs. Pet owners are no different, and shouldn't be made to feel guilty about the life enrichment they get from their animals. Just as we focus on lessening the impact of our computers and AC units rather than getting rid of them, we can do the same for our pets by feeding them a healthy but more vegetarian diet, getting them spayed and neutered, avoiding needless pet product consumerism, etc.
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Paleocon Posted 10:35 am
11 Jul 2008
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