First of all, if you installed the windows in 2019, you must claim any on your 2019 tax return, you are not allowed to spread the cost out over several years. Depending on the circumstances, you might be entitled to some extra credit if you amended your 2019 return, but you must delete the energy improvements from your 2020 return.
Second, the credit for windows is 10% of the cost up to a maximum of $200. The $200 maximum for windows is a lifetime maximum, and there is also a $500 overall lifetime maximum for all of the energy improvement credits including insulation, windows and doors, and furnace and air-conditioning. If you claimed any credits in the past, your present credits will be limited
