Whole-home standby generators (a Generac, for example) are installed to be a highly automated switchover power solution in a grid down scenario.
These are sized to run the whole house (all loads, so most likely a 24kw model), and usually by authorized dealers who do/coordinate everything for the customer. You get in bed with them for the life of the generator, and it's not a bad deal if your outages are generally small (a few hours, up to a half-day or so), and you live next door to the authorized dealer/service guy. These are tied in to natural gas or propane, so they can have extended run times, within their published guidelines for such run-times.
If you vary by even the slightest from their guidelines, there could be trouble ... takes careful reading of the manuals to stay within spec, and not have either the authorized dealer or the manufacturer get mad at you, and disallow repairs/warranties.
You'll see a good percentage of an affluent street in any given city that has such whole-home standby gen's sitting off to the side of the house. When an outage happens, they'll all fire up, and only their lights will be on compared to the rest of the street. A very few scenarios where even this solution might fail (natural gas supplier shuts down).
If you like the idea of a similar highly automated power solution based on solar components, you'll find it's a lot of work to get to that point, but it can be done. Lots of solar gear, lots of coordinated work, and an appropriate backup generator of some kind, and you can run some or all of your house off of a solar energy solution, for longer periods than a whole-home standby gen (which has some limits to run-times longer than 24 hours). It's just not as convenient as paying $20k or more to the generac folks via an authorized dealer.
Plenty of threads on this site if you want to go the alternate solar energy route to a whole-home standby gen.
Hope this helps ...
