This paper addresses an electricity conservation program (called "Doubléco") targeting small consumers, i.e. typically small companies in the service sector and residential consumers. The program was launched in November 2010 by the utility of the canton of Geneva (SIG); by the end of 2012, more than 50,000 participants had registered (out of a potential population close to 200,000). The program is mainly based on monetary incentives for participants to reduce their annual electricity consumption. The participants are also provided with information through newsletters and a website on measures for reducing their energy consumption and are given rebate vouchers for energy efficient appliances. In this paper we present the evaluation methodology (bottom-up type) that is based on a statistical analysis (treatment effect model) of historical annual electric billing information (2007 to 2013) of all participants and non-participants of the program. We find that the savings triggered by the program amount to 2-3% of the household's total electricity demand, while the respective value for small companies is smaller and much more variable (1-2% savings in year 1 and 2 but slight increase in electricity demand in year 3). Additional analyses are carried out to categorize the types of participants (regarding their support for selected energy strategies) and to address the durability of the savings and insights from research on communication and behavioural change.