In July of 2013 we had both windows and a large sliding glass door in the living room replaced in addition to a sliding glass window in the master bedroom. Immediate difference in the amount of noise from outside the house makes sleeping more peaceful and the living room more enjoyable. We're now able to keep the temperature around 75 instead of 80 degrees in the summer with an averaged $85/month electric bill. About a 20% savings in the gas bill in the winter A comparison from the electric company with our most efficient neighbors said we beat them out by about 15%. I've insulated the ceiling and the crawl space above this single story 1420 sqft so that has also helped to make it a great place to live. If we stay we'll do the remaining four windows. It's been a lot of bang for $4500 investment and led to other improvements as well. Thanks for a great product line.