Wow. We should have done this years ago.
We have a 2-storey house. In the summer, even though we closed all vents in the basement and main floor (in an attempt to get the cold air to our second floor), our basement was always freezing cold and the upper floors were warm. The air conditioner would run all the time on warm days. Now, after getting our ducts sealed by Aeroseal, all floors are the same temperature, and our air conditioner actually cycles off. I can't wait for the winter, when we typically have the opposite problem. I can only imagine how much money we are now saving. But the money is secondary. The comfort is priceless.
Aeroseal did a wonderful job. It took them all day, and in addition to sealing all the ductwork, they found broken and open ducts that they repaired on the spot. Very through and professional. They explained everything in detail, and the before and after results were dramatic. Highly recommended.