I had two pane windows installed in our single pane home. I wish I had had the money to do triple pane. It cut our electricity in half during the summer.
IF you want to save a LOT of Money, wait until there is a state fair or large county fair in your area. Then go to all the places that sell windows and fill out cards to win what ever they are giving away. That will cause you to be called by all of those businesses. Get a spiral note book and write down every window installer in the yellow pages on a different page. When they call for an appointment write it down and invite them over. If you get two at one time, that's great.
When they come to your door ask them who they are and make a show of finding them in your notebook. Some time during their presentation be sure to tell them that you are price shopping and for them to give you their best price. I always tell them that if they have the best price I will call them and have them do the work. But if they don't have the best price, they won't hear from me again.
The result: I had 14 people call me and 13 gave me a bid. (When the 14th one came over and I told him I was price shopping, he packed up his gear and told me he couldn't compete and he left.) The highest bid was $13,900. The lowest bid was $7500. I didn't like the lowest bidder, so I called the second lowest bidder and told him he was the second lowest bidder and if he wanted to look at his bid and revise it I would use him if he became the low bidder. He called me back in about 10 minutes and gave me a bid of $7000. I had him do the work.
I love my windows. I wish I could have afforded triple pane, but that's life. The point is that it was a pain (no pun intended) to have to deal with all those salesmen. But I saved $6990 over the highest price. That was worth the hassle.
Good luck to you and yours.