I'll suggest you look at natural gas fuel cell technology such as:
https://www.bloomenergy.com
especially if your looking at 24/7/365. Sometimes an option is a motor/generator/flywheel type system which gives the generator time to start. The fuel cell technology gives you the ability to use the waste heat too.
Many times the UPS system gives just enough power for an orderly shutdown or time for the generator to kick in.
Where I worked we had a 40 kW system that we quickly outgrew. It's primary purpose was ventilation. Secondary was toxic gas alarms and access control. The Fire alarm had it;s own backup power and so did most emergency lighting. In one lab, the lights were put on the generator.
We did one system that was put on emergency power for convenience. If the power failure lasted more than about 5 minutes, it would take a day to bring that system back up again. When we needed more power, it was the first to go.
There were also some large loads that were not put on the generator, but it could cost a day or more to bring those systems back online. If the outage was brief and we were there we could circumvent problems. Night mode was set so that damage was minimal. Again 15-20 minutes and your not there you have a lot of work ahead of you.
I wanted to create a small system that would have done an orderly shutdown, but it was vetoed. Some systems would have benefited by a pneumatic large valve
Only in one case, I used a UPS and that was to keep a "safety PLC" powered, so it could shut a system down properly which basically meant, a purge gas had to run for a short time and certain valves had to close.
For some reason, our company hated automation. We did basic research.