If all you need to power up is three scanners, use a small solar panel & a deep cycle battery. Will power up the scanners WAY longer than a ups feeding 120 VAC to a 12 volt power supply. And many UPS units put out TONS of RFI, especially in the AM broadcast band & up into 160 & 75 meters. Some MAY be clean, but I gave up after trying two different ones, YMMV.
Yeah, unless you specifically need to run something on 110 volts AC, there's not a lot of benefit to a traditional UPS.
Since the radios will run off 12 volts, you can make a pretty good system with a solar panel, charge controller and a battery.
UPS systems have a bit of efficiency loss to them. They have to take 110vac, convert it to direct current at the appropriate voltage for the battery pack, then convert it back to 110vac, then your scanner power supply converts it back to DC again. That generates some heat, some losses in the conversion, and all that reduces your battery run time.
A small solar panel and charge controller will easily keep a 12 volt battery topped off and depending on the size of your battery, run a whole lot longer than a consumer UPS will.