Passive damping of input filters in dc–dc converter applications has suffered enormous criticism presumably due to high conduction losses in the damping resistors. However, an accurate quantitative assessment of their adverse impact on efficiency is lacking. Similarly, not enough attention has been paid to the severity and extent to which they can effectively deteriorate a converter-efficiency under varying operating conditions. In order to quantify these losses we have performed a generalised power-loss analysis that helps in predicting this harmful effect of damping resistors on overall filter-converter system efficiency. A practical damping approach using a shunt R–C network, which is most commonly suggested in dc–dc converter applications, is investigated theoretically as well as experimentally. Results show that converter efficiency is susceptible to severe degradation, especially at high loads as well as at smaller damping resistor values. Furthermore, it is shown that these losses are considerably higher in buck-type converters than in boost-type converters. Authors emphasise that considering this negative impact on power economy is of crucial importance while optimising such a damping network.