I got this letter from the authorities in CT- as i applied for non grid tie inverter (Luxpower 5 kva) - on the app you can export to grid, that i dont use)

"Your application for Off Grid installation will not processed because you have used a City approved inverter. You can amend the application form for a non-approved inverter or apply on e-services for a grid tied hybrid SSEG installation."

i know i have a city app inverter -why do they ask for a non app inverter? and if i grid tie what is the monthly cost?