please do a search, been answered many times.
Oh...and I measured full output on my Yamaha running on propane and natural gas. Engine must have extra power to compensate for power loss.
So don't assume that you will not be able to get full power from your generator, this will depend on the generator itself.
I've been very happy with my tri-fuel generator...no draw backs in having fuel options.
Last power outage, lasted 48 hours (hurricane) plugged my generator into my natural gas line at home and cranked it up. Very happy.