In total, 181 ER20s have been ordered by 22 operators in Austria, Germany, Czech Republic, Romania, Slovenia, and Hong Kong. The first, and by far the largest customer was Austrian Federal Railways (ÖBB), which ordered 70 ER20s in 1998 and later acquired a further batch of 30 units.

The 140km/h Bo-Bo locomotives are powered by an MTU 16 V 4000 R41 engine providing a power output of 1.6-2MW and a starting tractive effort of 235kN.