General Electric ES40DC, ES44DC and ES44AC

For the EPA Tier 2 emissions standard, GE developed the new Evolution Series engine, also known as “GEVO”. By far the most successful variant, with almost 3,900 locomotives sold, is the ES44AC, the successor to the AC4400CW with three-phase traction motors. The Union Pacific is the largest operator with 1,234 locomotives, of which 296 are ES44AH with heavier weight of 432,000 pounds. For customers who still preferred DC powered locos, the 4,000 hp ES40DC and 4,400 hp ES44DC were offered. For Australian customers, the ES44ACi and ES44DCi were offered, which have better cooling.