5-8 years is fairly common calculation. 80% is the key. DEpends on the State. You are spot on. One thing to be careful of is calculated energy capture vs actual. I hope you are in AZ or Socal. There are online calculators to check your supliers promises.
One thing you probably skipped - cost of $ - but at 4% mortgage rate - even that is so low as to not count for much. (3% after tax deduction).
Painful to read this reporting though - I think he said the panels “created energy” about three times. Then the inverters “utilized” energy. But whatever.
Obvously you know what you are doing - the next step - if you have something to use it for - is CNG for vehicles. You should get about 1/2 of gasoline cost. +/- - without tax effects. might get a kickback for the compressor.
I have seriously considered putting CNG on my diesel pickup. On a diesel, you fumigate the intake with CNG and offset up to 60% of your fuel. If I get out in the middle of nowhere and run out of CNG, it goes back to burning 100% diesel.