Artificial Intelligence (AI) promises more convenience and comfort for our every day life in the coming decades. However, this does not come for free. Rebound Effects (Santarius, 2012) will lead to increasing consumption of natural ressources. Using service robots for home help as an example, we give a rough estimate for the size of these effects. The major contributor is the so-called “spare time rebound effect”. If the robot takes over household chores, its user gets additional spare time for further activities such as travelling, shopping, exercising etc., leading to a higher energy and ressource consumption in addition to the resources consumed by the robot. By establishing a common good balance sheet (Vogt & J¨apel, 2019) the ECG may be used to counteract the rebound effects. The external costs caused by robot use could be part of the VAT and a usage tax. Very interesting is the accounting of the spare time Rebound Effect. All activities of the robot owners during their newly gained spare time will be taxed accordingly via the ECG anyway. For social equity we suggest increasing duties to be paid on larger incomes.