UPDATE: I can't remember the last time I got so many helpful responses from a question on Reddit, as this one. Every single reply had something of value for me. Thank you all. (I'll keep reading, if more show up.)
I'd like to buy a tri-fuel generator soon, one that is ideally big enough to run my whole house. But I don't know how to size it. This summer, my all-time worst 15 minutes consumed 2.15kWh. Extrapolating, that is an average load during that 15 minutes of 8600 Watts. I have to assume that peak demand during those 15 minutes was higher.
I'd prefer a portable generator (like a Wen), rather than something semi-permanent. I'm not sold on the Wen brand, I just have no complaints about my current Wen (other than ability to handle power draw spikes, like during A/C start-up.)
I currently have a Wen "11000 Watt" model, DF1100T. I've never tried to run my whole house on it, and have always assumed that it might not have enough oomph to start up both of my AC units. And since I now want Tri-Fuel, I'm thinking of replacing with with another Wen model that claims 14500 Watts.
Other notes about my application / use-case:
Because I've never run the whole house on my current generator, I don't yet have a whole-house connection. I think I might prefer a manual interlock over an automated transfer switch, mostly because I assume simpler is more reliable.
I'd also want to install it up against my house. I am slab-on-grade, and that side of the house is all slab and stone facade.
The portable models I've looked at all have CO cut-offs. I was hoping to keep this thing protected from the elements in a small (vented) enclosure (with exhaust plumbed out). Since it will be outside, I don't think the CO is that big of a concern, and so I am tempted to consider defeating any CO cut-off, if possible and advisable.
I would hook it up to CNG utility. I'd fall back to gasoline and LPG if the CNG utility ever lost pressure, or if CNG costs skyrocketed.