The effect of group size on energy consumption by communal electricity users

A communal electricity metering, where several consumers split their bill equally without being able to distinguish between their individual electricity consumption (EC), may create a social dilemma. Using this concept as a frame of reference, we hypothesized that increasing the group size of the consumers would increase EC. We increased the perceived group size of communal electricity users and monitored EC before, during and after the intervention. We also studied interpersonal trust, collectivism, self- and collective efficacy, ECrelated attitudes, pro-environmental self-identity and self-reported EC. We found that during the intervention phase, mean EC increased by 28.9% - an increase that disappeared right after the intervention was terminated. The only significant predictors of EC were efficacy and trust. Selfreported EC was not correlated to actual EC. The implications for conservation of electricity in a communal metering setting and the caution needed when using self-reports of environmental behavior are discussed.