I'm a bigger fan of Dell desktop that companies have put out to pasture after a refresh cycle. They're very expandable, have plenty of horsepower, and the idle power draw isn't that bad. The better thermal characteristics compared to a laptop usually lead to very long life as well.
Related to a sibling comment, a decent UPS could power a Dell like that for a couple of hours if it's mostly idling.
Yes, I've got a Dell T3610 under the desk here now. My only beef is that it has weird Dell proprietary hardware, so I can't easily fit quieter fans to the PSU, or reuse the case with an ATX mobo
Related to a sibling comment, a decent UPS could power a Dell like that for a couple of hours if it's mostly idling.