Necessitated by the dwindling supply of petroleum resources, various new automotive technologies have been actively developed from the perspective of achieving energy security and diversifying energy sources. Hybrid electric vehicles and electric vehicles are a few such examples. Such diversification requires the use of power control units essentially for power control, power conversion, and power conditioning applications such as variable speed motor drives (dc–ac conversion), dc–dc converters and other similar devices. The power control unit of a hybrid electric vehicle or electric vehicle is essentially the brain of the hybrid system as it manages the power flow between the electric motor generator, battery and gas engine. Over the last few years, the performance of this power control unit has been improved and size has been reduced to attain higher efficiency and performance, causing the heat dissipation as well as heat density to increase significantly. Efforts are constantly being made to reduce this size even further. As a consequence, a better high performance cooler/heat exchanger is required to maintain the active devices temperature within optimum range. Cooling schemes based on multiple parallel channels are a few solutions which have been widely used to dissipate transient and steady concentrated heat loads and can be applied to existing cooling system with minor modifications. The aim of the present study has therefore been to study the various cooling options based on mini-channel and rib-turbulated mini-channel cooling for application in a hybrid electric vehicle and other similar consumer products, and perform a parametric and optimization study on the selected designs. Significant improvements in terms of thermal performance, reduced overall pressure drop, and volume reduction have been shown both experimentally and numerically. This paper is the first part in a two part submission and focuses on the design and evaluation of mini-channel and rib-turbulated mini-channel cooling configurations. The second part of this paper discusses the manufacturing and testing of the cooling device.