Well, FWIW, I have had propane regulators freeze up above zero, due to propane flow, and I have had tanks get too cold to evaporate enough propane. So, yes, the effect is real.
So...I think that you will be happier with bigger tanks, or tandem tanks, trying to run a generator. Those evaporation tables are a very useful guide, but they aren't totally accurate. Looking at the table, I can tell that Generator Joe didn't derated them correctly. A propane generator running at a 25% load does draw much more than 25% of the 100% column. Stick to the the 100% column would be my advice.
My other bit of advice is plan for a much longer outage than you think. It is the nature of the beast to have a bigger hurricane, or bigger swath of thunderstorms, or tornados, or... than you are used to. How will you have stockpiled enough fuel for that event? As a kid, we had a weather event that spawned a 150 mile swath of tornados and thunderstorms that took out half a state worth of power lines. We had linesman from all over the US come in to rewire the state. Fortunately, there weren't other major problems in the US at the time. It was the first time in living memory in that area that the power had been out for more than a day.
- Lucky item #1; at the time we were lucky to be a priority for the power company, but it still took eight or ten days to restore power. (I just remember that it was more than a week.)
- Lucky item #2; we had an extremely fuel efficient tractor, that we were able to turn down by about 50%, and had enough diesel to run it 16 hours a day. The kids weren't happy about no hot water, but we had food, and cooking gas.
- Lucky item #3 was an employee who lived twenty miles away who had power, and who had a backup PTO generator that was big enough to run everything that she was willing to lend us.
It could have been much worse. The PTO generator worked like a champ. Zero issues, and fortunately, we didn't need to cut and bale hay during the outage, so the tractor could crank away. But, yes, quite loud.
Just free advice: worth what you paid for it.
I should mention that I have a backup diesel generator. Why? Because I have lots of diesel fuel in use on the ranch, so I turn the fuel over, and diesels are relatively fuel efficient, so what I have on hand would last us a long time. I also have a backup backup gasoline generator, in case the diesel fails. (Which it has) I looked into propane, and for our needs, I couldn't see stockpiling enough propane. My next door neighbor went went the other way and just put in a 22kw Generac propane automatic standby generator, but then realized that her 500 gallon tank was only going to last two and a half days at full load. She's pouring a new foundation for a 2,000 gallon propane tank. She is seventy and her husband is eighty five or so, and not really up to lugging portables around. They are very happy with it. Two other neighbors have nothing and just toss their food out, and get by with candles. In an earthquake zone! But we won't go there. Different strokes for different folks. You need to do what works well for you, and your scenarios.
We are in the process of upgrading to whole house batteries and coupling our solar to batteries to have power that doesn't require stockpiled fuel. But we live in an earthquake zone, with wildfires, in a rural area, and with a truly substandard power company. It is the power company that "forgot" to pressure test their gas pipeline, and then blew up a suburban neighborhood, and has caused numerous wildfires in California. The one convicted of felonies. The one that has gone bankrupt to avoid paying for the damage their wildfires have caused. Yeah, that one. They also have trouble maintaining their power lines. Big surprise, right? I have had more outages in the last decade than in my entire prior life. Putting batteries in is NOT a cheap option, and we wouldn't be doing it without subsidies from the state (who gets a more reliable and greener electrical grid out of the program).
All the best,
Peter
