There are countless ways to reduce the energy consumption of your Atlanta home. Some projects pay for themselves in a few years and some take decades. Here is list of the of the projects with the fastest payback.
Tighten up your building envelope- Slow down the air exchange between the air you condition and the outdoor air. Weather strip the doors and windows. Take the cover plates off switches and outlets. Caulk around the box. If you are comfortable with removing the electrical fixture you can caulk the gap where the wire enters the electrical box. Replace the cover plate with a foam gasket type.
If you have a crawlspace or unconditioned basement, seal all penetrations between it and the floor above. You can use blocking, caulk or foam. Wear eye protection and gloves with long sleeves when using foam. Foam is the hardest thing to remove from skin that I have ever encountered. Do not seal the metal flu pipes as they need a 2 inch (double wall pipe) to 6 inch (single wall pipe) clearance to any combustible. These gaps can closed with sheet metal work. Repeat the same steps between the attic and any conditioned place below. Find out if your recessed can lighting is IC or insulation contact rated. If it is not then you will have to keep all combustibles 6 inches away or purchase a recommended housing to cover the fixture. If you have wood framed chimney it is important to seal these off at every floor change. If it is open the stack effect will draw air up and out of your house at a rapid rate. An open chimney bay is also a fire hazard as it will allow fire to spread faster between each floor level.
Seal any ductwork that is in an unconditioned space- Seal with foil tape and mastic all joints along the pipe, where the pipe attaches to HVAC plenum and where the pipe attaches to the register you see from inside the house. In the more inaccessible spots it is not uncommon to find ductwork that has separated in is just blowing your money outdoors. If your ducts have been replaced, the wall registers are often abandoned in favor of new floor registers. It is usually the case that the old registers are wide open and exchanging air at a rapid rate. Stuff them with fiberglass batt insulation, block them off and caulk or foam the smaller gaps.
Insulate all areas to at least local code level and exceed the code in the attic- Crawlspaces and unheated basements often have no insulation in the floor joist bays above them. Have them spray foamed by a pro or insulated with r-19 batt insulation. If you live in old house the exterior walls may not any insulation. This is harder to remedy because of the damage done opening up the walls. If your are doing a major renovation anyway then go the extra mile and get those walls insulated.
The attic is the most important area because of the stack effect and the high temperature differential. Remove as much temporary decking as you can so these areas can be accessed for sealing and remain open for the increased insulation depth. Where the rafter meets the overhang you will need to install baffles to provide a channel for air flow. Insulation often fills the joist bay and air can no longer move from the overhang to roof vents. Blow that attic with fiberglass or cellulose to a level that exceeds code. The code is r-30 here which usually equates to about 9 inches.
Replace single pane glass with double pane- There is a huge difference in efficiency between single pane windows and the most basic double pane windows. You can spend more on fancier double or triple pane windows but the smaller gains come often at steep prices.
Maintain your heating and cooling equipment- Have the equipment serviced twice a year or at a minimum change the filters regularly. If the system is old have it replaced with a more efficient unit.