The waste energy produced by under-floor traction equipment in MU stock can be used to heat passenger coaches. In many cases, the amount of thermal energy produced this way is sufficient to supply all the heating energy needed.

The use of waste heat can be realised by a heat exchanger (usually of the air-air type). This is already realised in modern DMU stock. In EMUs such a system is not yet implemented.

A more sophisticated method to make use of waste heat from traction equipment for comfort functions is based on the ORC principle. Such a system which is not yet realised in railways would permit to produce power for electric comfort functions from waste heat.