Green information systems have been shown to contribute to environmental sustainability and help to prevent associated problems. Private households account for 25% of primary energy consumption in western countries, and therefore hold a great potential to curb the use of fossil fuels and prevent cli-mate change. As such, green information systems should not focus solely on the organizational con-text, but also target a single individual’s behaviour in their home. Personal information systems (e.g., web portals) can achieve this focus, however, need to be actively used to produce effects. System us-age can be effectively motivated through incentives, and therewith contribute to positive outcomes. Incentives are either monetary or non-monetary and can be implemented in different scales. In a large field experiment (n= 2,355), with real energy customers of a utility company, we tested the effective-ness of different types and sizes of incentive in motivating active system usage. We show that incen-tives significantly increased system usage of participants, and additionally increased energy savings. However, monetary incentives were not necessarily superior to non-monetary incentives.