zzzBOX is an APU technology developed to replace current diesel operated APU systems. The device connects directly to the reefer unit, taps available power and converts it to free AC power to the cab. The company says zzzBOX is the first APU system that generates free cab power without heavy batteries or diesel, and offers a return on investment of just six months or less. It attaches to the underside of the reefer unit in less than one hour. It is solid state, weighs 50 pounds and requires no maintenance.