I agree with this. You can get a kit [1] to hardwire a UPS. You could then take the output of the UPS and run it into a subpanel with a separate 15 amp breaker for each room. That way you won't have extension cords, etc. which might only be rated for 15 amps drawing 30+ and potentially starting a fire.

1- https://download.schneider-electric.com/files?p_File_Name=AS...