The typical general aviation panel has changed dramatically over the last two decades. Whereas once the top of the line was vacuum-driven “steam gauges” and a couple of NAV/COM radios, today even 60-year old airplanes typically sport moving map GPSs and possibly even integrated glass cockpits. These new avionics make flying safer and easier, but they do add some new responsibilities for the pilot in command. That’s why a ground power unit (GPU) can be so valuable. These increasingly powerful devices make it easy to run your panel without starting the engine, depleting your battery, or running the Hobbs. Here’s how to find the right one for your airplane.