I borrowed a current clamp today to do some quick measurements on the 12V supply. I have the DC-DC output dialed in to 13.8V. The vacuum pump draws 125W while it runs. Sitting in the cockpit, power steering running, and dash blower on, the load on the system is roughly 440W. Turning on the lights, and specifically the high-beams increases the load to 700W. From there I turned on the wipers, blinkers, blower on high, and rolled down the two windows simultaneously and the load increased to 1100W. When the windows hit their limits, current peaked at 1380W. The supply I am using is rated for 1050W, so when the demand hit its peak, there was also some drop out of voltage from 13.8V down to closer to 12V.