what size external generator needed to run roof a/c


Junior Member
Hello fellow RVers ! I am new to the world of RVs and looking forward to camping and traveling!

We just recently purchased a 1989 Ford Fiesta Class B motor home / extra high top camper van.

It is nearly self contained except for a shower and generator (but has a place for a small one) , which I am hoping to install down the road (excuse the pun)

The camper van has a Coleman rooftop a/c unit.

Today I purchased a small gas stand alone generator 800 watt rated/900 watt max. ( a deal from Harbor Freight for $90)

I am hoping to possibly fit this into the door cavity where a built in generator may have gone. If not no big deal.

My main question is ..what is the minimum size / wattage output generator needed to run just the roof /ac or to run (instead) a fridge/freezer combo?

Im am not expecting this small generator to run all the 110 accessories at once, but would like to know if it will at least run one at a time?

prethanks for any and all help!

Looking forward to reading posts from this group!



Senior Member
Welcome to the RV world. Look at the specs. on the AC unit on how many Amps it draws, multiply these amps by 120 and you have the Watts needed. And remember the start draw is much higher than the run draw. Most likely a 2000 watt Gen is the minimum.