@Opus 17 @jmurphy-ectisp-n - i've enjoyed reading this thread.....
please note the instructions for the energy credit and specifically the instructions for Line 16.. it states the unused credit can be carried foreward to 2022; it does not state it can be carried back.
https://www.irs.gov/pub/irs-pdf/i5695.pdf
Line 16
If you can't use all of the credit because of the tax liability limit (that is, line 14 is less than line 13), you can carry the unused portion of the credit to 2022.
