Railpower Technologies, a subsidiary of the R.J. Corman Railroad Group, offers to rebuild existing diesel locomotives to new, energy-saving and environmentally friendly GenSet locomotives. The GG20B “Green Goat” is special since it is primarily being powered by batteries with a maximum output of 2,000 hp, while the batteries are being recharged by a 300 hp Caterpillar C9 diesel.

It has a smaller sister called GG10B of which only six were built. Of 55 GG20B built, Union Pacific was the largest operator with 21. Meanwhile, UP has passed them back to Railpower due to reliability issues. Also other operators have rebuilt them back to diesel switchers or GenSets. To test hydrogen technology, one GG20B was used by BNSF and the diesel engine was replaced by a fuel cell. It remained a one-off and was donated to the Oklahoma Railroad Museum in 2023.