You can run 12K in lights plus all your A/Cs and extra shit on a 21kW MQPower.
If you want to run a genny grow you need multiple generators so you don't have an interrupt in power when you pull your unit for maintenance. You also want a whole unit for backup. At least 3 to have it be 100% off the grid and reliable...
Fuel cell too, can't be hauling fuel to the site every day, there is a diesel delivery truck up here that comes to fill my cell for each grow and I smoke a few fatties with the delivery driver.
Even though these are WhisperWatt units, they're still loud and unless you put them in a pit or an insulated shed, or have a few hundred acres ( even then your neighbors will hear that shit..trust me ) every one is going to know you're running your grow on a generator because NO ONE needs to run one for that long to do what you'd do with one normally which is charging batteries...
PM me with any questions about my actual set up.