I have gas stove, furnace & hot water heater with NG which is why a 22kW NG unit will run my entire house. While sized for whole house in actual use I don’t run anything I don’t need just like I do when on electric utility power. Was on generator for 72 hours last summer due to hurricane. Cost me $84 above basic monthly gas bill/usage. As hot/humid as our summers are it was well worth it. All I did after utility power was restored was change oil & filter on unit then ready for next outage. I keep spare filters & oil on hand.
With that much gas service, I would be willing to bet a 12-16 KW generator would be sufficient to run everything you would need to during an outage. Nothing wrong with having the excess capacity at all, but if your budget is something you have to think about you could probably save over half the cost by installing a smaller unit up front and still be comfortable during an outage.
I don't think people realize how little load you actually put on your electrical system during 90% of the time but it wouldn't be more than 25%-35% for most people. Even with the newer all electric homes a load calculation is done to determine the size of the electrical service by most reputable electrical contractors, but there is still only so much a person can use at any one time unless you have a pretty huge house and lots of equipment you run at the same time- which in my experience is very unusual. In my experience, at peak times even a large house will seldom pull more than 100 amps on their electrical service at any one time and most people only pull half that or less even at peak times. These are the factors that need to be taken into consideration when considering your installation in relation to your budget. During an outage, most people will scale back a bit on power usage in any case- I've found it's just human nature...
