The wife and I just purchased a new home with a 400 amp service. I have a caterpillar 45kw prime single phase generator, currently hooked up to existing home(200 amp service),wich I would like to hook up to the new house for standby power during storms. Is this generator big enough for my house or should I look for a larger one. I would like it to run the whole house and not just certain circuits. Not that I would turn everything on during a storm, Just like to have it if I need it.I am aware that a 400 amp transfer switch will be needed. I am curerently looking at the asco units, It is what I have now and has worked like a charm. Any help would be apreciated? Thanks.

Big enough?? I'd say so!

45kW is 150 amps @ 240v continuous. Even a McMansion can run on this. Like you said though, you have to be conscious as to what you run. Like I would not run a whole house tankless water heater for instance.
It also depends on how many people will be living in the house. Sadly, many mini mansions only have 2 or three people living in them.

BTW, can I borrow a few thousand dollars?

Of course not knowing the size of your home, what type of heat or air conditining, how many walk in size coolers you may have, and that, Now it should huge, I have ran my entire house on one 1/3 that size, but then why do you have 400 amp service,

The OP probably has a wine cellar, a heated inside pool and a hot tub.

Thanks guys, sounds like it will work fine.
As much as I would like it to be, there is no pool, hot tub, walk in cooler, or wine cellar. It is 4,600 s.f. though, with two 5 ton a.c. units. Gets a little hot here in Texas.

Once again appreciate the help.

Thanks for the feedback!

......, but then why do you have 400 amp service,It's hard to get around these days with these large homes. Just the number of circuits alone is usually enough reason. Typically the demand load calc is well above 200A.