Replies

1. 
   DavidThomas | Sep 20, 2002 12:48am | #1

   Clearly, Option B will use less electricity. The A/C won't run as much during the day. You could get a programmable thermostat and have it turn on the A/C 20 minutes before you get home - savings AND complete comfort.

   Same in the winter, let the temps go down when you are not there. Turn it back to 70F when you return, or have a programmable thermostat do it for you.

   Savings would be in the order of 15-20%.

   David Thomas   Overlooking Cook Inlet in Kenai, Alaska
2. 
   BillHartmann | Sep 20, 2002 01:09am | #2

   While I agree with Dave there is one factor that he has left out.

   HUMIDITY. If you are in a high humidity area then when the AC is not running the extra mositure is not being removed. That might make it uncomfortable enough that you drop the thermostat.

   Get a humidity gauge and monitor it.

1. 
   TLRice | Sep 20, 2002 02:56pm | #4

   " If you are in a high humidity area then when the AC is not running the extra mositure is not being removed. That might make it uncomfortable enough that you drop the thermostat."

   Bill,

   I disagree with what you said. Acually, the opposite is true. The reason is, that in moderate temperatures in a high humidity environment, it is much better to have a temperature "setback". Let the house warm up and then have the A/C come on and run for an extended period of time. MUCH more effective at drying the air than the unit constantly cycling on and off over the day to maintain a temperature. Although another subject entirely, this is why oversized AC units create clammy enironments and waste money.

   David,

   David Thomas gave you the best answer. The most energy efficient and most comfortable way to operate your system is with a programmable thermostat. The cost is about $40, that will probably be recovered the first month of use. See the part above about dehumidification. When it is not very hot, but plenty humid, about the only way you can dehumidify is making the AC run for an extended period, like 45 minute to an hour, as opposed to 15 or 20. Also, if you are not at home during the day, spending the money to heat or cool the house to a comfortable temperature when no one is there is a waste. The programmable themostat in my house has a "5 and 2" type of program. Weekdays (the 5 part) has 4 settings; wake, leave, return & sleep and weekends it has only wake and sleep settings. You can change the temperature manually, but it is nice to have the furnace warmup the house before you wake up and really nice to have the AC kick on as you're driving home from work. I recommend and specify programmable thermostats in all HVAC systems I design, residential and commercial.

   Tim

   Edited 9/20/2002 8:18:55 AM ET by Tim

3. 
   TomMGTC | Sep 20, 2002 05:19am | #3

   It depends on the type of system. My geothermal system runs more efficiently when left at a constant temp. Takes too long to recover from wide temp variations but will maintain very efficiently. .