Running ac off of generator while driving.

I was shuttling Class A's in Phoenix on Monday and the dash air did nothing to combat the heat. Turning on the gen and roof air took care of the heat. Wednesday I took a Winnibago Vista across the desert and having the gen and roof air on was a must. The other nice thing is when climbing mountains the dash air can be turned off to keep the engine temp down while still having the roof air going. This was very nice while climbing the mountains outside of San Diego.

Assuming 6.5 mpg and 65 mph, that's a total of 10 gallons of fuel burned per hour. The generator, running the roof A/C, burns about 0.5 gal per hour. Drops my overall mpg from 6.5 to 6.2

Your numbers may vary a bit, but the difference in fuel burned is negligible for the comfort provided.

MrWizard wrote:

as far as gas milage for the drive engine
it has NO effect
but since it does use fuel for the genny
your next fill up means more fuel from the pump to the tank
but this is NOT engine fuel mileage, this is additional overhead fuel use by the genny for 'personal comfort'

we get people on here, saying i used my genny for the roof top A/C and mileage went down,
NO your engine mileage did not change

You are of course correct, my "engine" mileage doesn't change. But my "motorhome" mileage does. ;) The easiest way to quantify the fuel consumption and comfort while driving WITH the generator/AC vs WITHOUT the generator/AC is to compare apples to apples; i.e. mpg to mpg.

And it is comfortable when you arrive at the days destination. Otherwise you need an hour or two to catchup.

Those that worry about mileage should not be driving an RV. It’s great to know your average MPG to help budget for a trip but that’s about it. We use the dash air mostly until it gets uncomfortable. Then crank up genny and run roof air. The other day it seemed that once the roof air kicked in the dash air got colder. Must have been sucking in the cold air from the roof unit.

We do, but only when the house gets uncomfortable. Maybe around 80-85 degrees, depends on humidity. Our Onan 4,000 manual says .7 gallons an hour under load, don't know how accurate that is but after a 6 or 7 hour drive we're only talking 5 gallons or so. It helps if you don't care about mileage, I used to, tracked every mile and gallon and finally made a conscious decision to not worry about it. Momma is happier when she doesn't get hot while she sleeps the whole drive , LOL.

On one Class A coach we had, it had close to a "cockpit" for the two captains seats. The dash air would keep that part of the coach comfortable but the rest of the coach got pretty warm.
We ran the generator to power the roof air so that the entire coach was comfortable when we stopped for lunch or when we got to the RV park to stay for the night.
The fuel usage for the generator was negligible for a coach that already got poor mileage. Our comfort when we parked was more important.
Some people install a "shower curtain" like structure behind the seats so that the dash air keeps them comfortable. I always thought that it was better to cool down the whole coach especially since we had a large dog that liked to wander to the back of the coach while we traveled and, like I said before, we wanted it cool when we stopped to fix lunch..

We use it regularly if the dash AC can't keep up. This can happen if the coach is sitting in the sun for too long or the humidity is too high. It's a bummer I can't use both ACs while driving :( however, it is usually ok it just takes longer to cool down. Our QD6000 generator can't run both 13,500 BTU ACs. I'm thinking of installing an Easy Start unit to see if that helps. I do know both of my ACs won't run on a 30 AMP shore power connection the coach draws just a little to much power if you factor in other loads.

i use my generator and roof top A/C as needed
it does not affect engine motor directly
IF you dash a/c has too work less hard, then maybe there is a slight difference
in engine power

as far as gas milage for the drive engine
it has NO effect
but since it does use fuel for the genny
your next fill up means more fuel from the pump to the tank
but this is NOT engine fuel mileage, this is additional overhead fuel use by the genny for 'personal comfort'

we get people on here, saying i used my genny for the roof top A/C and mileage went down,
NO your engine mileage did not change

this is like saying the water bill to fill your swimming pool went up, because you has a pool party and all your friends drank too much beer and keep using the toilet

in our experience running the genny in order to use the coach AC has no effect on the MH engine power and negligible effect on MPG. we run the dash and house AC on hot days and it really helps keep the coach cool.

I use my gen. when running down the road. It is the best way to keep your coach cool in the summer. The amount of fuel you use is dependent on the gen size. I have a Dp 2002 Dutch star and it is more than reasonable for fuel on running air conditioner plus I run the fridge as well.
Ray