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10/01/07 Elizabeth Elephant suggested this challenge and received 30 votes before it was promoted.

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Challenge Details

Hot enough for you? According to the Old Farmer’s Almanac, we’re in the dog days of summer. That’s the brutally hot part of the season when seas boil, wines sour, dogs grow mad, and everything else living slows to a sweaty crawl or slow slither. The sun is high in the sky and the days are long. Locusts buzz, asphalt softens, and children beg for freezer pops. Sounds like an ideal time for that technological marvel — air conditioning. But instead of refrigerating your house enough to make you put on a sweater in July, how about cooling it just a little less, saving some electricity, and cutting down on your carbon emissions? You and the kids can still have the freezer pops.

This Featured Challenge is based on a number of great Challenge suggestions from our Challenge Workshop. We particularly want to give credit to Elizabeth Elephant, meriicheri, and jacky4president_60546 for their Challenge suggestions.

The Carbon Connection
It takes a lot of energy to cool things down. So it should be no surprise that refrigerators and air conditioners are the biggest users of electricity in the typical American household. Air conditioning alone is responsible for about 16% of the average household’s annual electricity bill. That comes out to nearly 2800 kilowatt hours (kWh) of electricity per year for homes with central air conditioning and 950 kWh for households using room air conditioners (i.e., window units). At an average nationwide cost of 10 cents per kWh, that average air conditioning system costs $280 to run each year. Many systems cost much more.

Of course, how much you use air conditioning partly depends on where you live and how many days a year you need your home cooled. New England has short summers. A home in New England with central air might only use 1500 kWh per year. However, Florida can be downright hot most of the year. A home in Florida with central air might use over 4000 kWh of electricity each year. And the more electricity you use, the more carbon dioxide gets released into Earth’s atmosphere.

Remember, electricity most often comes to you from power plants that burn coal, oil, or natural gas as fuel to generate electricity. Burning that fuel releases CO2 into the air. So in terms of your own personal carbon impact, the biggest users of electricity have the greatest negative carbon impact. That average American household central air conditioner uses enough electricity each year (2800 kWh) to cause the release of over 2 tons of CO2 into the air.

Getting It Done
One way to reduce the carbon impact from air conditioning is to do without. However, that sounds drastic — and honestly rather uncomfortable. Using the air conditioner for fewer hours can cut down on the amount of electricity it uses. So can turning up the thermostat. Each degree higher you set your air conditioner’s thermostat allows it to use 1 to 3% less electricity.

Need help meeting this Challenge? Here are a few suggestions:

• If your house or apartment has central air with a programmable thermostat, you won’t have much problem carrying out this Challenge. Simply raise the temperatures that you already have programmed for the summer months by two degrees. For example, if your thermostat is set at 74 degrees F. during the day, you want to raise that to 76 degrees.
• If you don’t have a programmable thermostat, get one! It will control your furnace in the winter and your air conditioner in the summer and allow you to use the right amount of heating or cooling when you want it. For example, if you aren’t home during the day, don’t use the air conditioner! Don’t believe the old myth that leaving the air conditioner on all day, even while you’re away, uses less electricity than turning it on when you get home. Not true! Program the thermostat to turn the air conditioner on an hour before you get home. The house will be nice and comfy and you will have saved hours of wasted electricity cooling the house for just your philodendrons.
• Some room air conditioners (window units) also have programmable digital thermostats. However, if your room air conditioner does not have a thermostat with specific temperatures, just do your best to turn the Hi/Low or Warmer/Cooler settings so that the air conditioner runs a little less.

There are many other ways to reduce your electricity needs during the summer. Here are a few other ideas for keeping cool and reducing CO2 emissions:

• Help your air conditioner run more efficiently. Clean or replace your air conditioner’s air filter every month when it’s in use. The harder the air conditioner has to work sucking air through that filter, the longer it runs and the more electricity it uses. If possible, put your room air conditioners in windows that are either facing north or are in the shade from trees or an overhang. A window air conditioner that is sitting in direct sunlight uses 5% more electricity than it would if it were shaded. For other ideas on making the most energy-efficient use of your air conditioning, see Mr. Electricity’s 32 Super Tips for Saving Money on Cooling.
• Work with the weather, not against it. In many parts of the country, nights are cool even in July and August. If the air temperatures outside gets colder at night than the temperature set on your thermostat, then you are better off shutting down the air conditioner and opening the windows. Buy a thermometer so that you know the air temperature outside. When you see it’s cooler outside the house than inside, it’s time to open those windows.
• Fans are your friends. A ceiling fan doesn’t use much electricity and the added air circulation it provides can help you keep your air conditioner set at a higher temperatures. Make sure the ceiling fan is reversible and that it blows down in summer and up in winter. Window fans and floor fans also make you feel cooler by getting the air moving or by helping move cooler outside air into the house at night. A large fan running for 24 hours might only use 2 kWh of electricity. Your central air uses 42 times that amount! Clearly it’s OK to run that second fan. How do you keep cool in the summer and still save on electricity? Have you tried any of these methods yourself? What sort of difference did you see in your electric bill? Share your experiences with fellow Rallyers in the Discussion section below.

Rules of the Challenge
This Challenge asks you to raise the temperature setting on your air conditioner by 2 degrees for one week. For instance, if you normally have your thermostat set at 74 degrees, you would raise that to 76 degrees. Those of you who have window air conditioners without digital thermostats will need to approximate by turning the cooling setting “back” a click or two. Carbon credits for this Challenge are for one house or apartment; if members of your team all live in the same place, only one of you should sign up and take credit for this Challenge. This Challenge is repeatable until the AC season in your area comes to an end.

Learn More
Energy Savers: Air Conditioners
Yahoo! Green: Keeping Cool Indoors
13 Free or Cheap Ways to Keep Your Home Cool This Summer

See the Math
Due to the big differences in how people use their air conditioning in different parts of the country, the numbers were a bit harder to crunch this time around. Let’s look at the known or estimated numbers being used for this Challenge:

• According to the Department of Energy’s Energy Information Administration, the average American household (house, condo, or apartment) with central air conditioning used 2796 kWh of electricity in 2001. A household using window air conditioners used an average of 950 kWh.  source
• However, the above numbers are a national average. And we all know that people living in Tallahassee, Florida need air conditioning more hours a day and more days a year than they would if they lived in Nashua, New Hampshire. So we’re striking a balance and spending our statistical summer in the Heartland. For the purposes of our calculations, we are using data from EIA’s East North Central region, which includes Indiana, Illinois, Michigan, Ohio, and Wisconsin. The average household in that region used 1621 kWh of electricity for central air conditioning or 712 kWh if they had window units.  source
• No matter where you live in the continental United States, summer is still summer. And that means that the months with the greatest needs for air conditioning are June, July, and August. For Atlanta, 24% of the energy needed for cooling is used in August. For Dallas, that number is 22%. And for South Bend, Indiana that number is 26%.  source
• In the East North Central region, 71% of the households with air conditioning have central air and 29% use window units. Based on those percentages, we will use a weighted average of 1356 kWh of electricity used per year for cooling in the East North Central region, which includes South Bend.  source
• Now let’s calculate the amount of electricity used for cooling by the average household in South Bend in the month of August. Multiply the weighted average yearly electricity use for air conditioning (1356 kWh) by the percentage electricity used for air conditioning in August (26%), which gives you 353 kWh.
• Setting your air conditioner one degree higher allows your air conditioner to use 1 to 3% less electricity. Let’s average that number to 2% per degree and then double it to 4% since the Challenge asks you to raise your thermostat by 2 degrees. (Feel free to go for more! If you normally run your central air at 73 degrees and raise your thermostat by 5 degrees to 78 degrees, you could save up to 15% of the electricity you would normally use for cooling.)  source
• Applying the 4% savings to the 353 kWh of electricity normally used for air conditioning in August gives you a savings of 14 kWh, or 3.5 kWh per week. At a national average of 10 cents per kWh, that’s a dollar savings of $0.35.
• On average, generating 1 kWh of electricity results in 1.55 lbs of CO2 emissions.
• Saving 3.5 kWh of electricity therefore reduces carbon emissions by 5.4 lbs of CO2 (14 kWh x 1.55 lbs CO2/kWh) for the week.

We know all of you Rallyers don’t live in South Bend, so your numbers will vary. (And don’t worry! We’ll run a heating Challenge next winter and you can all iron out the regional scoring inequities!) No matter where you’re drinking your lemonade this summer, we think you’ll find that 2 degrees warmer isn’t that big of a difference to your overall comfort. Try 4 degrees, and see if you can live with that. Over an entire year of cooling, you could be save hundreds of pounds of CO2! And that’s a chill that fits the Rally bill.

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