I've also been weighing in on backup generators, for a while. I am a big Honda proponent, and I wanted to fuel with propane, so the only thing I could find was made by Winco. Not inexpensive, but it qualified for my checklist. As I weighed the decision to commit to the purchase, I got to wondering about multi-use. I do not know enough about the topic, so perhaps the Winco has me covered, but I considered that I might want to arc weld, if I have that much generation available to me. Which led me to Lincoln, who sell a propane-fueled Kohler-powered welder that also acts as a backup generator.

I haven't had to empty my wallet yet, so it's all still theoretical, but if want to weld, would I need a generator designed to feed a welding machine, or would anything with enough generating capacity suffice?

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I have a small propane Onan genset. Regarding propane as a stationary engine fuel in say a generator. Its a first rate fuel....it does not go bad, I have found propane engines to be able to sit unused for a long time and they fire right up. If you have those big tanks 800-1000 gallon or something like that I would consider a propane back up generator. Now having used one when I first went off grid,as that's what I thought I would use for battery charging in December, within something like the first month I said to hell with this and went to a gas generator.In 20, 30 even 40 pound tanks I found fuel consumption by volume (you have to consider the tank too,) to be to much, and it was to much lugging around the small tanks, then there was the problem of filling, out in the country, there is only one country gas station in 15 minutes where I could get propane, and only then if the one guy they had trained to pump it showed up for work. It was just a pain in the ass. I havnt used those generators in years. My propane is now dedicated for the kitchen stoves where it performs stellar. Just my experience with using the stuff.
I can recommend the Lincoln welders, I have a old Ranger 8 with a Honda engine, but only a gas unit, not propane.
I will tell you this though now that I am running a inverter that can source 10,000 watts (though 5000 would be plenty) I wont be using a generator for welding, I did a lot of welding last summer to test things out and I don't need to fire anything up to weld so consider that...money put to solar may get you the same benefit. my 2 cents.

Though if you want just a generator to run a separate welder like any of the newer inverter stick welders in the 100 to 180 maybe 200 amp output range a 5000 watt continuous generator would be your starting point, larger is ok but not less than 5000 watts for moderate welding. Though I have used a Honda eu2000 with a miller maxstar 150 stick unit in the up to 80-85ish amp or so range welding (from memory), the little Honda was working though!

I thought I would add just in case by welding you mean, serious industrial capacity like running 1/16 dual shield flux core all day or burning 1/4 inch rods then 10,000 watts plus is your starting point, as just a home gamer type welder I don't need any welder either in wire or stick with greater than 150 amp output, though the higher output machines have better duty cycles, but even with them I don't dial em past 150.

I thought I would give this one warning though about the Canadian tire champion brand, its the 4000 watt peak, 3000 continuous model. I bought one of these years ago just to run a little maxstar 150 at under 100 amps, the POS should have ran it, it had the engine capacity, and generating capacity...It would not even light up the smallest rod I had no matter how low I set the output...Turns out the problem was the output regulator,Just a bad design, the damn thing folded back the output voltage every time I tried to strike up...I could not hack my way around the problem, the regulator was full potted....so be aware because welding is one of the hardest things you can ask your generator to do, if you do have a problem investigate the regulator, on some you can make adjustments to increase rotor current. The gererator works perfect for everything else, just not what I bought it for.

Excellent info Peppercorn, thanks. I never really thought about fuel consumption, my thought was to plumb it into the main propane feed for the times I would use it, maybe mount it on a skid so I can make it mobile, if necessary. I don't know much about welding, but it seems like a skill I'd like to develop, so that's why I was thinking a fuel-powered welder might be a good idea.

I would have thought the amp draw on a battery pack, for welding, would stress it quite badly? I think I have enough solar panels to do the trick, but the battery bank I'm seeing in my mind's eye, to weld, is huge.

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You are not welding off your batteries, but mostly off your solar panels, Free power. I will assume for anyone with a off grid house you will have at least 2000 watts of solar power very likely much more as panels are so cheap now days.
For much of the welding I do my arc voltage is roughly 23 volts at 100-120 amps So that's 2760 watts, if 2000 watts is coming in what am I drawing from my batteries. 760 watts...less than a coffee maker, less than a microwave, less than a hair drier, would use. Of course for simplicity I am ignoring Some system losses to make a point, but you see what I mean. If you go larger in panels so you have a 3000 watt system then your welding would be all sun powered.

Welding takes less power than I thought. When I read "100-200 amps, I had always thought that was at 220V or something LOL. So weld in the daytime, when the batteries are topped up and the sun is shining. A welder is not such a big deal any more, so long as I can wait for the sunshine. Thanks.

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Welding takes less power than I thought. When I read "100-200 amps, I had always thought that was at 220V or something LOL.

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The job of the welding machine is to take that high voltage 120-240 and step it down to the 20-30 volt range for welding, and to step up the amperage. You cant weld at those high voltages your electrode would be blasted away on contact, though there are processes where those voltages are used to cut steel but that's a different thing than welding.

Just stumbled across this, a guy who uses a small generator off grid to weld with. Note that he says you need a 6 kw unit to weld up to 200 amps, that is roughly in line with my experience, previously I was saying 5kw up to 150 amps at the arc. Also note he is mig welding I believe with 035 flux core, no way he needs the power of a 6kw unit for what he is doing (035)though. I have welded 035 flux core, and a 5kw (5000 watt)generator has been just fine. https://www.youtube.com/watch?v=t1mxxo_4p7I