Understanding the pros and cons of COTS versus custom power supplies helps engineers make timely, defensible decisions about products they implement in their projects. Commercial applications often involve standard form factors and controlled environments. Operating space and power draw aren’t critical. Conversely, military applications often require unique form factors to ensure proper fit on the platform, precise weights to maximize flight longevity, and strict center of gravity requirements, as well as near-infallible reliability to preserve human lives. Each application is different; what remains constant is that power supply parameters already have been figured into the engineer’s design.