Systems and methods are directed to providing power to a transport refrigeration system (TRS) using an undersized main power source in combination with a secondary power source. The systems and methods allow the undersized main power source to be used with a TRS that requires a power more than a maximum threshold power of the undersized main power source to operate at a full cooling capacity. The secondary power supplements the undersized main power to allow the TRS to operate at the full cooling capacity. Optionally, a tertiary power source can supplement the undersized main power source, or the undersized main and secondary power sources to run the TRS.