CT, 6 contractors out of the 30 or so and nobody will even talk to you about home owner installs/labor. You need the manufactures certificate for the tax credit and all that I've contacted will not give it unless it's professionally installed by somebody they have licensed.
The site you cited [nrel.gov] gives the same numbers as I have about 26kw of panels gets me 29kwh annually and would cover my entire south facing roof. 2kwh a month current usage or 24kwh a year and some wiggle room to charge a EV later. Sure if you lived in a smaller home in a better area for sun the numbers change quickly.
We differ greatly on panel cost I show complete ready to mount panels at around 150 a pop out of china.