By the way, it’s not a government rebate, it’s an income tax credit.
Virtually all windows are energy star windows. The demand is for energy star windows so the plant doesn’t change the assembly line back to old technology with thinner glass, non gas injected spaces, to make a couple of sub standard quality windows. They just leave the energy star sticker off of the energy star window and charge less.
All you need is the energy star sticker if your taxes are audited. Check with a home builder and get a set of stickers from a new home construction. The contractor doesn’t get a tax credit for new construction, and should be willing to give the stickers to you, rather than throw them away.