i have pulled off a sizeable grow with a diesel gen running off veggie oil in the country with neighbors too far off to hear or smell shit all...worked for me...and free fuel is cheaper than grid power.
Maybe you did...but you weren't burning 80 to 100 gallons/week like p0opstlnksal0t is talking about.
I happen to know "a bit" about generators...and they are just not practical to be used as a main power source for a decent sized grow....and using veggie oil just adds to the headaches!
And when I say "decent" then I am talking decent enough to off-set ALL the cost (and headaches) associated with a Genset grow...it's just not gonna happen.