This paper analyzes the effect of supplying feedback by text messages (SMS) and email about electricity consumption on the level of total household electricity consumption. An experiment was conducted in which 1,452 households were randomly allocated to three experimental groups and two control groups. Feedback was supplied throughout 2007 to members of the experiment groups who accepted the invitation, and data on consumption of electricity for 2006 and 2007 collected for all participants and control group members. 30% of the households invited to receive feedback accepted the invitation. Results suggest that email and SMS messaging that communicated timely information about a household's 'exceptional' consumption periods (e.g. highest week of electricity use in past quarter) produced average reductions in total annual electricity use of about 3%. The feedback technology is cheap to implement and therefore likely to be cost-effective.