These were three electric locomotives with which the Prussian-Hessian State Railways tested the new type of traction for use in front of express trains since 1911. The requirements for the test locomotives were a continuous output of 700 kW and a speed of 100 km/h with a few express cars on the hook. For the purpose of comparability, all three received the chassis and body from Hanomag, while the electrical part of the ES 1, ES 2 and ES 3 came from Siemens-Schuckert, AEG and Bergmann respectively. The wheel arrangement was 2-B-1 and therefore asymmetrical, although the vehicles were bidirectional.

The ES 1 was designed for 110 km/h, but could reach up to 135 km/h with the bogie in front. Although the continuous output did not reach the required 700 kW, it was able to pull a 240-tonne train at a constant speed of 100 km/h. The ES 2 nominally had a slightly lower maximum and continuous power, but was able to achieve a higher tractive effort. Compared to the first two, the ES 3 had a significantly higher power and had a wooden structure, but could not convince due to persistent problems in the electrics.

The test drives with the three locomotives took place on the Dessau-Bitterfeld route, which was one of the first with the 15 kV and 16⅔ Hz power system, which is the most widespread in German-speaking countries today. They continued until the outbreak of World War I in 1914. The ES 2 was the only one of the three locomotives that was able to make it to the Reichsbahn and was in service on the Wehratalbahn for a few years. There it was designated E 00 to illustrate the pioneering role of the Prussians in electric traction.