But now you must know the current draw of your computer and monitor in order to have an inverter capable of handling the load. Add those two and you have 340 watts of draw. A 350 watt modified sine wave inverter will be maxed out, but can handle the load for an hour at a time, usually. It is much better to have an oversize inverter, say a 500 watt unit, than heat up and destroy the only inverter you have. Check out the wattage draw of your own computer and monitor.
Printers are a different story altogether.
Although it is difficult to draw generalizations on printer power requirements, many printers can draw 420 watts of power all by themselves. It is possible to use a 3 hp horizontal shaft gasoline engine to turn a 65 amp alternator, charge two 12 volt RV batteries, hook up a 1000 watt inverter, then be able to run the 'puter, monitor and printer. But that is overkill for the simple purpose of keeping in touch via computer, and a bit expensive. There aren't enough fumes to get paranoid about, but it would be negligent of me not to mention it. Obviously a draft with opened windows is desirable if the battery is inside the home.