800w Inverter genny $149, sale ending today

towpro wrote:
I used to maintain a fleet of trucks that ran on Propane, and had a conversion in an olds Delta 88 myself that was dual fuel.

It does take more propane than gasoline to go the same distance. in fact its about
20% more propane.
But propane runs so much cleaner. And since you don't need to atomize propane to get it to burn you can run your idle lower
But propane was harder to start in the dead of winter. In my Olds conversion I would have to switch over to gas when parking it so I could get it to start the next morning.

Well that was the guy's point - that you can't just use the BTU energy of the fuel to straight-up calculate the additional fuel required and/or less energy produced by the fuel (which is what that chart in your link is doing). There are a lot of other factors, like the quality of the gasoline, the a/f of the burn (is it 100% efficient at), etc. He claims that the carbs on these generators are pretty inefficient. But, again, he's in the business of selling propane conversion kits.

I don't have any scientific data, or any real anecdotal data either. I finally got to use my newly-converted generator in a real power outage a few weeks ago. The power was out for nearly 11 hours starting at around midnight. It was a school/work day so I fired up the generator on natural gas (the kit allows you to do both, adjusting the fuel supply with a load block). It ran for about 8 hours with varying loads. Now natural gas is 35% less efficient on paper, so my 8,000 running watts would theoretically only be 5,200. But, according to the watt meters on the transfer switch I was pushing close to 7,000 watts during peak spikes (toaster, hair dryer, coffee maker in addition to both furnaces, fridge, lights, etc.). I could hear it bog down as you might expect, but it delivered consistent power.

I would agree that you're going to give something up by moving from gasoline to LP or NG, but I don't think it's the 20-35% that the BTU differences would suggest.

EDIT: And in an attempt to bring things a bit closer to the original topic, I would much prefer gasoline for a portable generator - particularly the small one in question. In my motorhome? I dunno, I still think I prefer gasoline. The propane gets eaten up quick enough without adding the generator to the mix. (and now back off-topic again...) But at home, it's NG/LP hands down. We didn't have power for 2 weeks after "Superstorm Sandy." The gas stations couldn't pump the fuel out of the ground because there was no power, and those that could get gas to the pumps ran out immediately because delivery trucks couldn't get through. We siphoned gas out of every one of our vehicles to keep the generators going (the 85 gallon tank on the Allegro was key). It was a semi-apocalyptic event that I don't want to repeat. Natural gas was never interrupted - the generator could have theoretically run non-stop. If natural gas were interrupted I now have 1,000 gallons of propane (that won't go bad).