douglas d20 rooftop air conditioner, 9800btu 12v, black, no idle, battery powered complete unit douglas ___complete system ready for install__pre-charged (r134a)_ douglas presents the d20 - a revolutionary rooftop air conditioner. the d20 is a unique no-idle 12v system that can be powered by a smart auxiliary battery bank (which can offer no-idle cooling when the vehicle is off); the unit can also run directly off the vehicle’s power. with this ultimate green alternative, you can save thousands on fuel cost, vehicle maintenance, and downtime by simply reducing your vehicle's idling. connect to a power outlet when available with shore power and use your unit and charge vehicle batteries all in one, under $300. shore power sold separately (asin# b074cplw2f). .