It depends on what you are buying them for. Here is how to think about it without the sales pitch.
Replacing windows that are drafty, single-glazed or sealed-unit failures usually reduces how hard your heating and cooling work. How much you save depends on the windows you are replacing, the rest of the building envelope, and how you use the house. Anyone quoting you a guaranteed percentage is guessing.
The change homeowners mention first is not the utility bill. It is the room that finally stays usable in January, the draft gone from the chair by the window, and how much quieter the front of the house is on a busy street.
Windows are one of the things buyers and inspectors look at. Visibly failing windows become a negotiating point; sound, consistent windows remove one. Treat it as protecting the sale rather than as a return you can bank on a spreadsheet.
Rotted sills, repainting, storm windows, plastic film every autumn, and repeat repairs all have a cost in money and weekends. Replacement ends that cycle for a long stretch.
If the windows are sound and the problem is one broken balance or worn weatherstripping, repair it. If you are selling in a few months, get advice before spending on a full replacement. We will tell you when waiting is the better move.
Call and describe the windows. We will tell you whether it is worth doing now.
No forms, no waiting on email.