The SD70MAC (colloquially known as a "Mac" or a "70 Mac") is very similar to the SD70M and SD70I, the main difference being that the SD70MAC uses AC traction motors. AC motors, while simpler and more reliable than DC motors, require expensive inverters to generate a variable-frequency AC signal, raising the locomotive's purchase cost substantially. The majority of SD70MAC models were produced with 4000 horsepower (2,980 kW) EMD Model 710 prime movers, while later-production SD70MACs are rated at 4300 horsepower (3,210 kW) and feature SD45-style flared radiators. They were also offered with a head-end power generation system for passenger trains.

Over 1500 examples of this locomotive model were produced. Purchasers include Burlington Northern (now BNSF Railway), Conrail (engines now owned by CSX Transportation), CSX, TFM/Kansas City Southern Railway and the Alaska Railroad.