Add your feedback: what’s the best strategy for summer cooling?
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Last year, we turned on our air conditioner twice. At times it was a little hot and sticky (here in the Boise, Idaho area it tops 95° pretty much every day in full-on summer), but in general, Daniel and I acclimated to it pretty well and didn’t mind much.
Other people… well, that is a bit trickier. My sister lives with us, and her boyfriend often spends Friday and Saturday nights here (on the couch!), and they were both extremely uncomfortable last summer. I felt kind of bad about it, but we offered to let them run the A/C and pay for the additional cost, and that didn’t go over so well.
This year, I’m working from home (not in a building air-conditioned to about “frigid”), and I’d like to figure out a happy medium—something that will keep the fam happy and still keep the bills reasonable. I think that a big part of this will just be to actually get up and close the windows when it gets hotter outside than inside (I love fresh air, but it’s sensible to keep the fresh air limited to the night and morning hours in this case).
What I’m really wondering about is air conditioner efficiency. For instance, right now it’s 87° outside and 82° inside, so only a 5° spread. I can’t image it would cost much to keep it 5° cooler inside (vs. outside). But what about days when it’s 100°? I’d like to know what kind of curve the air conditioner efficiency has as related to inside-outside temperature differences. For instance, if it costs, say, a dollar per hour to cool the house to 10° below the outside temperature, but $2/hour to get °15 lower, that would be worth knowing. (I’m sure those per-hour numbers are way off, but you get what I’m saying, right?)
Another thing is that I saw this “Cool-n-Save” gizmo. It seems pretty smart; it cools the A/C unit itself with evaporation. A study showed it cut the cost of air conditioning by up to 30%. However, I don’t know how much the air conditioner costs to operate, so I’m not sure whether the Cool-n-Save is worth $80—the break-even point would be when the air conditioner has accrued a cost of $267. I’d be surprised if we use that much, just because if we get next month’s bill and it’s about $80 (and the others who benefit from A/C opt not to contribute), I’d expect it to pretty well stop.
The truly aggravating thing about this is that I feel completely uninformed. I don’t know the best way to use my air conditioner, and that annoys me. So please, by all means, enlighten me! If you don’t know anything about air conditioner efficiency, no worries: I mostly want to know how other people handle the cost/comfort balance. What do you do in the summer?
I have done or am stilling doing the following:
http://frugalforlife.blogspot.com/2005/05/cool-your-home-and-your-spending.html
- Use a fan
- Look for leaks
- Use shades
- Use the thermostat wisely
**Worn a wet t-shirt around to keep cool (this is with the curtains closed of course)
**Worn a wet towel around my shoulders and neck
**Stuck a bowl of ice in front of a fan
**Gone to the mall to just have a few moments of air-conditioning
**Drank lots of water to keep my body temperature down
In the May 2006 issue of Cargo they had an article called “Easy being green” (page 60). In the article there were a lot of money saving ideas. I am in the same boat with the A/C. In the article they spotlight a air conditioning product called the Mobile Master Evaporative Cooler. I would suggest looking into the unit. The cost is about $330 but costs only pennies a day to operate. You should also be able get a tax credit for the price. You can’t beat that! If you decide to do a writup on this please email me the link. Good Luck!
Opps forgot to post their website.
http://www.adobeair.com/
Devices like Cool-N-Save are based on increasing the efficiency of your central air conditioner’s outdoor condensing unit, through evaporative cooling. Evaporative cooling occurs when water is sprayed on the condensing unit. However, water causes mineral deposits. And any potential savings are offset by the costs of the device, the water and removal of resulting mineral deposits. But mineral deposits are nearly impossible to remove without damaging the condensing unit. Over a period of years, mineral deposits ruin equipment. So, the long-term result is lower efficiency, higher operating costs and pre-mature equipment failure.
In Boise’s dry climate, a better approach is to use water in an evaporative (swamp) cooler. Swamp coolers cost next to nothing to operate and by design, cope with mineral deposits much better than your existing air conditioner. However, swamp coolers tend to be controversial since they increase humidity, airborne particles (pollen – dirt) and require windows to be left open slightly to exhaust air. Then again, some people prefer higher humidity and fresh air to central air.
Adequate insulation, attic fans and shade are very cost effective. Of course, so is your approach to raise the thermostat set point. You should be able to determine an approximate percentage of savings by searching the internet.
Addendum: Evaporative coolers should be sized for the whole house – not individual rooms. So called “mobile or portable” coolers do not work well. Mostly, they increase room humidity until the air is saturated and feels like a wet blanket. A whole-house cooler’s capacity is based on total cubic feet. Cooler capacity is rated in cubic feet per minute (CFM). So, a 1,500 square foot home with 8 foot ceilings would be 12,000 cubic feet / 2 = 6,000 CFM cooler capacity (it is customary to exchange all of the home’s air about every two minutes).
To decide whether you want to run your A/C you have to decide how comfortable you want to be. The perceived tempurature a person feels is based largely on humidity. The main thing to remember is the body cools itself thru evaporation. The higher the humidity at a given tempurature the warmer a person feels because the body moisture does not readily evaporate.
Evaporative coolers, as mentioned above, add humidity to the air. Now in a dry climate that may not be a problem. However even in Boise one has to assume the humidity may rise, say during a thunderstorm on the hottest day of the year. Again, the higher the humidity, the less evaporation takes place which means less cooling is achieved.
The advantage of a central air conditioner is that as the air conditioner is running it is removing water from the air, thus lowering the humidity. If the air conditioner is sized properly you can run it at a higer temperature and still feel cool because it has lowered the humidity in the air.
One mistake many people make is to wait until it is hot in the house before turning the a/c on. This will not properly remove moisture. A properly sized a/c unit will maintain a temperature and cycle on and off. It is not designed to lower the temperature, especially on hot days, say in the mid 90’s and up. If you set the a/c unit at a desired temperature and allow it to come on when that temperature is reached it will run for a while and then, if working properly, shut off for a while. It will continue doing this unit the heat load in the house has decreased. (i.e. the outdoor temperature drops). However if you wait until it gets unbearable in the house and then turn the a/c on it may run the rest of the day without shutting off, especially if it is very hot outside.
The cost to operate an a/c unit will not vary (much)per hour by how warm it is outside. (Unit amp draw does increase slightly the more load it is under, such has being hotter outside.) The hotter it is outside the longer the unit will run thus costing more, but the per hour of operation cost will not vary much. A kilowatt of power will cost the same no matter how warm it is outside.
By keeping the house at the desired temperature all the time, instead of turning it off and on, is the most cost effective way to operate it. Also, if you are lucky enough to live where the temperature drops at night, open the windows and let the night time air cool the house, then close them in the morning before the outside air rises above the inside temperature.
I would venture to guess that by running your a/c it will cost somewhere between 10 and 20 dollars a month. Most people spend more than that going out for dinner. That estimate depends on how cool you keep it and how warm the summer months get. And that also depends on your utility rate. Ours is around 4 cents a kilowatt.
I would suggest to set the a/c at a reasonable temperature (somewhere between frigid and sweltering) and let the system do its job. Opening the windows at night and closing them in the morning will help keep the costs down. Not allowing the heat to build up in the house will improve the quality of your sleep as well.
Happy summer!