Windows in Arizona have to answer to sun first and storms second, except where the town reverses that order. West and south glass in the low desert turns a room into an oven by late afternoon, and the night does not always give the heat back. High country glass has the opposite complaint: a draft, a failed seal, and a frame that takes real cold. Monsoon rain then tests every sill that dust has packed shut. Name the exposure and the town.
Look at the failure you actually have. Fog between panes means the seal is done. A frame that feels soft means water has been in the wall, often at a stucco joint or a sill with no slope. A window that will not lock is hardware, not a full replacement, until the frame is out of square. Dust that filters in on a windy afternoon is a gap problem. One stuck sash in a guest room is not the same call as every west opening on the house.
Ask whether the work is an insert into the old frame or a full-frame job that opens the wall. Inserts are quicker and they leave a rotten frame in place, which is a mistake in wet stucco. Full-frame work shows you the rough opening and lets the flashing be tied into the weather barrier. Ask who finishes interior trim and exterior stucco. Ask how the sill sheds water. A pretty unit with a flat sill will leak on the first hard monsoon.
Heat and cold both punish seals, so ask what was specified for the whole unit, not only the glass. Do not expect a lecture about a utility bill. Expect a straight answer on drafts, broken hardware, and water at the stool. Older desert houses still have single panes in aluminum, and some mountain cabins still have wood sash that swells. Say which you have, and how many openings are part of the ask.
Bring a count, the rooms, and whether the frames are soft. Arizona will keep baking the west wall and, in the high country, freezing the north wall. Call the number on this page.