GE ES44AC

The General Electric ES44AC (or simply, "GEVO") is a energy-efficient, 4,400 hp locomotive which was first introduced into full production in 2005, with the first ES44AC prototype built in November 2002. The ES44AC is the direct successor of the AC4400CW, which could not be produced domestically after 2004. Like EMD, GE had to essentially design a new locomotive to comply with EPA Tier 2 standards. Unlike EMD, GE had to give its new locomotive a new power source; the 7FDL16 prime mover was replaced with a more efficient prime mover, the GEVO12. Only a handful of production units operate with this engine. Most newer units have a completely reworked 7FDL-16 prime mover.

The ES44AC is selling very well, far surpassing EMD's output. The ES44AC has a few other variants. The ES44C4, introduced in 2009, has seen the most orders from BNSF. This type of ES44AC is a standard model, rather with the outer two axles of each truck being powered and the middle axle of each truck being a trailing axle. Another variant is the ES44AH, ordered by CSX, (classified as CW44AHs by the CSX, similar to their designation for the heavier AC4400CW predecessor) and as of late 2014, the Union Pacific (UP calls them C45AHs.) These units are weighted to 432,000 lbs compared to the usual 415,000 lbs. CSX's version utilizes GE's Radial Steering trucks. The Union Pacific has continued a tradition with their ES44AC locomotives as they have done with the AC4400CWs, in which they have been ordered with "Controlled Tractive Effort" for DPU service. Which brings the final designation to "C45ACCTE." The -45 in this case, does not indicate horsepower, rather it distinguishes these newer units from older AC4400CWs.

The ES44AC is selling very well, far surpassing EMD's output. The ES44AC has a few other variants. The ES44C4, introduced in 2009, has seen the most orders from BNSF. This type of ES44AC is a standard model, rather with the outer two axles being powered and the middle axle of each truck being a trailing axle. As well as the ES44AH, ordered by CSX, (classified as CW44AHs by the CSX, similar to their designation for the heavier AC4400CW predecessor) and as of late 2014, the Union Pacific (UP calls them C45AHs.) These units are weighted to 432,000 lbs compared to the usual 415,000 lbs. CSX's version utilizes GE's Radial Steering trucks. The Union Pacific has continued a tradition with their ES44AC locomotives as they have done with the AC4400CWs, in which they have been ordered with "Controlled Tractive Effort" for DPU service.

The ES44AC in Late 2011 was reworked to meet EPA Tier 3 standards which went into existance Jan 1st, 2012. There are no visable changes. However in August 2012, GE released its Tier 4 ES44AC prototype, this locomotive looks very different from a Tier 2/3 ES44AC. GE is now in the process of building 20 more Tier 4 ES44AC's. Tier 4 regulations started on Jan 1st , 2015. This Tier is the final and most stringent of the standards. Several Tier 4 ES44AC's are testing on the UP over Donner Pass and in the Powder River Basin. Tier 4 ES44AC's retain most features of previous ES44AC's, but they have raised "humps" in the middle, as well as a larger, more sloped radiator in back with two cooling fans. These require more space in the car body for Exhaust Gas Recirculation equipment. It has been confirmed that production units will not have the "humps" in their carbodies. GE currently rosters six Tier 4 ES44AC demo units (GECX #2015, 2020-2014). Only #2015 has an official paint scheme of blue, white and green, while #2020-2024 have a basic solid blue scheme. GECX numbers 2021 and 2024 are testing on the Union Pacific.

In 2013, GE built an LNG (liquefied natural gas)-powered ES44AC, GECX #3000. This unit is equipped with a NextFuel LNG conversion kit, and is currently used as one of two units in BNSF's GE LNG test set (the other unit is BNSF 5815, an older ES44AC also equipped with the NextFuel kit). 3000 and 5815 are separated by a BNSF LNG fuel tender.