"NetKev" writes:

My rational for the UPS solution was that since the printer runs at
450 watts when printing, then, say a 600 watt (1000VA) UPS battery
would act as a buffer during the high load times. Doesn't this make
sense?

No. The printer likely does not draw enough current to drop the
voltage low enough for the UPS to switch to battery operation. So the
UPS will do precisely nothing, but the load will still cause your lights
to dim slightly. The printer probably works fine down to 95 V or so,
while your lights will visibly change in brightness with only a few
percent change in line voltage.

There are UPSes that provide line voltage regulation via a multi-tap
transformer. But they only adjust voltage for the device downstream.
The lights are upstream of the UPS, so they'll see as much voltage
change as ever.

The right way to fix your problem is to run a new circuit for the
printer, one that doesn't share wiring with any lights.

A simpler fix: print large documents just before going to bed.

Dave