our 10kw QD Onan burns at least 1/2 a gallon an hour...i think its a bit higher but
havent measured it <yet>.
its rated to burn up to 1 gallon an hour iirc.
our home/portable has burned close to 2 gallons of gasoline per hour (full tilt, 2 pool pumps & other stuff)...its a northern tool unit....when not at full tilt it still sucks the better part of 1 gallon per hour (and its LOUD...i DONT recommend it).
I bought the fuel conversion kit from these guys -
Generator Conversion Kits to Propane and Natural Gas.
ive never measure the consumption - was just happy to have it so that i didnt have to worry about getting gasoline during another hurricane.
the northern tool unit is NOT a welder...i have a sep hobart mig that i use in my garage & i have a 30a outlet on the wall for it....during a storm i pull the utility supply/main on my breaker panel & then back feed thru the garage/welder outlet.
regarding the RV fridge - my experience has taught me to cool the fridge (at least initially) via ac current...it cools down MUCH faster...and then i switch to propane or automode while traveling.
the consumption of propane by the fridge is close to immeasurable from what i can tell -
and friends of mine w/ travel trailers (w/ twin 20 or 30 lb tanks) have said the same, running their fridge consumes next to zero propane.
ive learned that i dont need to run the fridge as cold as i thought....settings 1 or 2 in moderately warm (80s) weather keep everything cold and prevents frost build up.
initially evne in 100* weather i was keeping the fridge on 4 - and even on a long 3 or 4 day weekend camping i could build up frost on the cooling fins inside the fridge.
i used to turn the fridge on 24 hours before i needed to load things in it (on propane)....
on a/c i only need about 6 maybe 8 hours to cool the fridge down before loading it.