I have ran both desktops and laptops from a 12V/24V DC to 120V AC inverter on both 12 and 24 volt systems with absolutely no problems. They actually do not draw that much juice from an inverter. I run my laptop on a small cigarette lighter plug inverter in my car.
Or... One could make their own DC power supply cable for laptop (proper polarity important!). Most will run on 13-14 volts DC. Power supplies for laptops are rated 120 AC in converted to 9V-20V DC out. The computer is actually not that picky about a couple volts either way. Done it and tested it many times.
Thanks, I knew that may laptops ran on 18-20 volt power supplies.
The normal desktop has multiple voltage requirements inside the system.