$18-$22 a piece.
As for tips on temperature, it's really a question of humidity since most A/C units have a dehumidifier built in to get rid of all that sticky-icky moisture in the air. For us, we tend to crank the A/C to a comfortable 78 degrees F on really hot days and wait for the outdoor temps to drop to around 80 degrees F. 2) We can also vouch for using fans instead. Also, using lightweight fans throughout the apartment will allow you to turn up the A/C a few degrees. [Via What Else Can I Do to Bring Down Bills in the Summer?] 3) Invest in a programmable thermostat. They really don't cost that much, but letting the computer do all the thinking for you can lower bills significantly if you're the type that tends to forget the A/C is on. 4) Use natural cooling. We know some of you aren't early birds, but if you are, opening up all the windows in the house early on, then closing them around 9AM or so will keep the cold air in. Keeping the blinds closed are a biggie, too! Readers have also suggested double lined sun blocking curtains. 5) Clean and maintain your A/C unit. Fill gaps along the sides of your air conditioner to keep outside air from leaking. Remember to clean air conditioner filters regularly and keep the front and back of air conditioners unobstructed. We don't know how many times we've seen a pile of leaves covering an A/C unit's intake, driving down its efficiency tremendously. You can also check out our post earlier last month for some more tips from our readers!