I have 3000 square feet on the main floor with a 1200 square foot basement. I am in Northern Alabama, we had 498 cooling degree days last August. The house was built in 1959 and the insulation in not great. I have a 3-year-old 5Ton 12 SEER heatpump for the main floor that has been modified to provide hot water (this provides all my summer hot water at no cost, and boosts the efficiencey of the AC somewhat). I have a 1.5T 12 SEER unit in the basement that rarely runs in the summertime. Family of four. Ceilings are 8'2". I also have a large hot tub that is not exactly cheap to run. I have an electric clothes dryer that seems to run 24/7. Water heater is also electric (but most of the water is heated by waste heat from the AC in the summer). Gas stove and ovens. No one except me turns off lights in the house, but I am the one who liek the house 72 in the summer (68 in the winter). At one point, I had compact fluorescent lights in about 90% of the light fixtures, after constant complaints I have swiched over to halogens in most fixtures (it does look better than the fluorescents but at almost 8 time the energy cost.)
The heat is combination heatpump, electric strip and natural gas. The heatpump is by far the most economical of those, so I tend to use it the most. I switch over to gas when the outside temperature is below 20 degress. Natural gas prices have tripled in my area in that last 3 years, and are going up again.
The year after I installed the 12 SEER heatpumps I was able to cut my electric bill over 25%, I am not as diligent now and things have crept back up.
My electric bill for August was 3800kWh or $250. That is about the peak for the summer. During milder months the electric bill is around $125. Winter electic also runs about $250 in cold months. Garbage, water, sewer, spinkler system, gas and tax add about $100 in both winter and summer (more water in the summer, more gas in the winter.)