on a 100 degree day, would it matter for efficiency, whether to set the thermostat at 79, or 70 degrees?

your air conditioner goes by the temperature inside of your house, and it will run continuously until that temperature is reached. Then it will only come on to maintain that temperature. You should set the thermostat at night, because it is more efficient to maintain the temperature than to try and drop the temperature 20 or 30 degrees.

Sure do!

It takes hours to heat up or cool down a home in extreme conditions, so if you don't have a programmable thermostat, I recommend that you get one.

With a programmable thermostat you can preset your temperature settings to when and at what temp you want your heat or ac to come on.

What usually works is for a person to set the morning temp so it saves you energy while you are away by either raising or lowering the interior temperature when everyone is expected to be gone and setting a normal temperature @ two hours before you are expected to return from work or your kids to arrive home from school.

It takes time to heat or cool down a home so if you prefer comfort and convenience I recommend you remove the screws that hold your thermostat to the wall and take a piece of paper and make a diagram of the back where the wires come in, colors and number of wires, AND the codes for the connection points for these wires, then go to your local home or hardware store and see their selection of programmables that will match the configuration for the thermostat you currently have.

Once you have this information you can decide whether to do a change over or not provided you are willing to do the work to make your life easier.

The longer the A/C runs, the more it cost. The difference between the two settings could run into a LOT of money over the period of a month. Set it at 78 and be done with it.

today my roommate and I closed the ac vents in one of the less used rooms in the house and the overall temp of the other rooms dropped noticeably. also today our high temp outside was 98, we turned the thermostat to 78 and it still felt like 74 (where its usually set) in the open vent rooms. hope this helps.

set it to the higher temperature. it will save electricity which you won't have to pay for.

it's really just the humidity that makes you uncomfortable,