Lowe’s Window Installation Service. If you’re wondering what the average cost to replace windows is, Lowe’s can help. Lowe’s offers window installation as well as many types of new windows to choose from. Our window brands include Pella, JELD-WEN, ReliaBilt and United. Contact your local Lowe’s to schedule a free consultation with a , The national average window installation cost is $2,650 per project. Here are some examples of average trim repair and window replacement costs: Trim repair: Line and case a window frame with an MDF product: $400. Line and case a window frame with raw hemlock wood: $500. Approximate cost to install five windows at one time: $3,000., The average cost of a window installer is $23 per hour in Dallas. Keep this figure in mind when budgeting your window replacement. Whether your windows are old, damaged or not as energy-efficient , , , .