Suzanna Blake with the US Sun online magazine, wrote a Flueblocker article on how to save money on Summer A/C costs.
Growing up in Wisconsin taught me quite a lot about air sealing and insulation for the winter months. However, living the last decade in the hot humid latitude of South Carolina has taught me a lot about weatherproofing for the summer. This Flueblocker article covers some of the methodology that is similar in both states, but the goals tend to be different to beat the heat.
The high energy use months are May through September in the South.
My focus in Wisconsin was keeping my natural gas bill down in the winter. If you are interested in another US Sun article covering low hanging fruit of heating savings in drafty Wisconsin cottages, you can look at this story.
Here in South Carolina my focus is bringing my electrical bill down in the summer. And considering I am running a 2400 sq ft, 2 story, 4br, traditional stick built in 1985 on about $50 per month electrical bill. I would say I have found a good deal of success. The Flueblocker article in the US Sun covers how I managed to do it.