The Charger is powered by a Cummins 16-cylinder QSK95 4-stroke high speed diesel engine, which meets United States Environmental Protection Agency's more stringent Tier 4 emissions standards that took effect in 2015.

Four Insulated-gate bipolar transistor (IGBT) power inverters carry electric current to each of the four AC traction motors.

[4] In response to a 2013 Request for Information from Metro-North Railroad, Siemens said they would be capable of producing a dual-mode variant of the Charger with onboard energy storage for use by Metro-North and the Long Island Rail Road, as well as intercity service on Amtrak's Empire Corridor.

[13] The Charger series competes with other Tier 4 compliant locomotives, such as the EMD F125 and the MPI MPXpress MP54AC.

[17] In February 2017, Amtrak and the Washington State Department of Transportation began testing one of the Midwest-bound SC-44 locomotives along the Cascades corridor in the Pacific Northwest for federal certification.

[20] Testing at up to 135 miles per hour (217 km/h) was conducted at TTC and on the Northeast Corridor in September 2016 which resulted in federal certification for 125-mile-per-hour (201 km/h) operations.

[21] Revenue testing on the Capitol Corridor and San Joaquins routes in Northern California began on May 25, 2017.

[23] The Northern California units were formally accepted and approved for solo service on October 23, 2017.

[32] California regional commuter line Altamont Corridor Express ordered four SC-44 locomotives in April 2018, with deliveries beginning in December 2019.

[37] Compared with the SC-44, changes were made to the ALC-42 to make it more suitable for long-distance service: additional positive train control systems for nationwide service, a larger 2,200-U.S.-gallon (8,300 L) diesel fuel tank (instead of 1,800 U.S. gal [6,800 L]), a larger diesel exhaust fluid tank, a larger sandbox, a more powerful 1,000-kilowatt head-end power generator (instead of 600 kW), an extended nose section for easier repair in the event of minor front-end collision, and a prime mover de-rated to 4,200 horsepower (3,100 kW) to lengthen maintenance intervals.

Each ALC-42E will be paired with a special trailer car that will have equipment to support electric mode on the end closest to the locomotive, and a passenger seating area on the other.

[46] The Illinois Department of Transportation (IDOT), in conjunction with its counterparts in California, Michigan, Missouri and Washington, purchased 32 SC-44 locomotives for state-supported corridor services, operated by Amtrak under contract.

[55][56] The locomotives are used in pairs, bookending four passenger cars (expandable to seven) on Brightline's Miami–West Palm Beach service.

[60] In June 2018, the North County Transit District Board of Directors approved the purchase of five SC-44s for its San Diego-area Coaster commuter rail service, replacing five older F40PH locomotives.

In January 2022, Montreal's Exo ordered ten Siemens Chargers to update the fleet.

[65] MARC announced in August 2015 that it was seeking $58 million to purchase eight locomotives to replace their aging electric-powered AEM-7 units, with deliveries planned for late 2017.

[54] The first MARC Charger was shipped from the Siemens factory in early December 2017, and began testing in mid-January 2018.

[68] In December 2020, New York's Metropolitan Transportation Authority (MTA) approved a Federal Transit Administration-funded contract for 19 dual-mode locomotives based on the Charger design.

[77][78] In February 2024, five locomotives were purchased for use on the Trinity Railway Express (TRE) commuter rail service operating in the Dallas/Fort Worth area.