Department of Defense Energy Security Act of 2014

Department of Defense Energy Security Act of 2014 - Amends the National Energy Conservation Policy Act to authorize agencies to enter into energy savings performance contracts to reduce the costs of fuel supply, delivery, or transport for nonbuilding applications.

Prohibits payments by agencies to entities that supply, deliver, or transport fuel under such contracts from exceeding the amounts that the agencies would have paid entities without the contracts.

Authorizes the Assistant Secretary of Defense for Research and Engineering to: (1) carry out research to improve military vehicle technology to increase fuel economy or reduce fuel consumption of military vehicles used in combat; and (2) establish an online, centralized repository for all Department of Defense (DOD) operational energy-related research and development efforts.

Directs the Secretary of Defense to establish: (1) a DOD executive agent for warrior power to align and advance efforts to measure and manage the development and evaluation of man-portable tactical power generation systems to power tactical communications equipment, weapons systems, and other troop equipment; and (2) a program to foster secure and reliable sources of energy for military installations, including incorporation of advanced energy metering, renewable energy, energy storage, and redundant power systems.

Establishes in the Treasury the Department of Defense Alternative Fuel Vehicle Infrastructure Fund to support installing, operating, and maintaining alternative fuel dispensing stations for use by DOD's alternative fueled vehicles and other infrastructure necessary to fuel the vehicles.