Compared to steel car bodies, aluminium coaches are substantially lighter. Some experts stress that part of the corresponding energy gain is lost by increased energy demand for comfort functions due to less efficient heat insulation properties of aluminium walls. Although no figures are available, it can be assumed that there is still a considerable energetic net advantage of aluminium over steel.

The mass reduction effect of using aluminium instead of steel for car body construction can be estimated as follows:

The car body accounts for about 20% of the total mass of a conventional MU. It is assumed that replacing steel by aluminium yields a maximum mass reduction potential of about 20-30% of the car body weight. The overall effect on vehicle mass is therefore around 5%. The corresponding overall effect on energy consumption is of about 1 % in main line and about 3 % in local and regional operation (cf. the following elasticity table).