The CyberPower CP350SLG is a good small uninterruptible power supply. Its only rated for 250W and it only has a few minutes of battery life. Not suitable for a big computer. But it’s perfect for backup power for network gear, like a router or a modem or the like. And it’s pretty small, just 7x4x3 inches. I made a mistake and bought APC’s small UPS first and the damn thing is ungrounded, which is ridiculous and dumb. I’ve had better luck with CyberPower UPSes anyway and this small one is exactly what I needed.
I’m a big fan of small UPSes. I don’t need something to carry me through a 30 minute power outage, I just want some backup that will keep my equipment running if the power drops for a couple of seconds. Because PG&E, you know? It’s a shame there’s no DC power standard, I bet you could make a DC-only UPS 1/4th the size with a lithium battery. But instead it’s all lead-acid batteries and producing 110V AC just to be transformed back to DC by all the equipment its powering. (That APC UPS does have powered USB ports, a small step towards DC UPS.)
Some day I should look into whole-house UPS units. A quick look suggests it’s about $2500 for 2.7kW, plus installation. This discussion suggests $10k is more realistic if you really mean a whole house.