An energy efficient household is one of the solutions in the approach to create a green society because the quantity of electricity being consumed in households is rapidly increasing. In this paper, we report on the implementation of an electricity consumption metering and online visualization system installed in 30 households with the objective of encouraging behavioral change. The system provides the following information about each household: 1) electricity consumption, 2) cost, and 3) CO2 emissions. Each piece of information is refreshed at one-minute intervals. This type of information is stated has having the potential to change people's behavior toward electricity conservation. The system comprises three main parts: 1) an electricity consumption data metering, 2) storage and processing, and 3) information provision. The metering part measures the electricity consumed via sensors set in the electric switchboard in each household. The data storage and processing part stores the data from the metering part and processes the three types of information. The information provision part provides the information to households via websites on the Internet. To test the effect of information provision on behavioral changes, we conducted an experiment comprising two phases: 1) before information provision and 2) after information provision. Each phase was conducted over two weeks, after which we compared the amount of electricity consumed before the information provision with that consumed after to provide quantitative results. Further, we evaluated each household's conscious change toward electricity consumption to provide qualitative results. The results show both quantitative and qualitative changes for some households. Consequently, we also investigated what types of information drove their behavioral changes.