Napa is a very high cost-of-living market — pricing guide and permit rules below.
Napa window replacement rates: $5,000-$18,000 per system. Always get 3 written quotes and verify CA licensing at California CSLB (cslb.ca.gov). Sales tax on materials: 8.5%.
Napa requires permits when work exceeds $500 or involves full system replacement. Your licensed contractor pulls the permit — if they ask you to pull it, that's a red flag.