Why is the AUTOTHERM ERS system called an energy recovery system?

Because the systems take waste energy from another process (combustion to propel a vehicle) which would normally be lost (dissipated to the outside air) and recovers it for a useful purpose (to heat the passenger compartment).

At the same time AUTOTHERM ERS systems are energy conservation systems as well because they reduce fuel consumption by eliminating the need to idle in order to keep vehicle interiors warm in winter.