Should I use a laser printer with a UPS?

Only if must. Laser printer uses up a surprising amount of power (due to heated rollers), and will discharge your batteries faster than you expect, even on standby. If you do, make sure UPS is rated for the power of printer plus computer plus monitor. It doesn't do any good to have your computer brown out as soon as printer starts to print. Ink jet printer, on the other hand, uses a surprisingly low amount of power.