The existing 25 kV AC and 750 V DC equipment has been retained with a hydrogen fuel cell added, currently taking up one of the carriages.

In September 2018, Porterbrook announced it would develop a hydrogen fuel cell demonstrator in partnership with the University of Birmingham's Centre for Railway Research and Education.

[7][8][9] In June 2019, it was announced that approval for mainline testing of the unit (branded as HydroFLEX) had been granted after a period of demonstration at Rail Live 2019.

The next phase of the development of this prototype is move the hydrogen tanks and fuel cell from one of the carriages and suspend them beneath the train.

[11] A second unit was presented at the COP26 Summit at Glasgow with one of the DT car's passenger doors removed and permanently sealed.