Since I added 3/4" of rigid foam insulation and a tyvek wind barrier and re-sided the house...

Plus replaced the AC and Furnace and water heater all with highest efficiency I could afford...

Even with the Air on... even during winter. We nearly never pay more than $200/month for everything. One month, we had the air on it was high 90s for a long while... *AND* my wife was canning peaches and other stuff... total was about $300...