This paper analyses the environmental implications of considering renewable portfolio standard (RPS) in power sector development in Indonesia during 2006-2025. An input-output analysis was carried out to examine the CO2 emission changes in the whole economy. There are four main factors that affect the CO2 emission changes, i.e., fuel mix effect, structural effect, final demand effect and joint effect. The results show that the CO2 emission sin the whole economy would be mitigated by about 6.1%, 12.6% and 17.8% if RPS levels of 5%, 10% and 15% are considered respectively during 2006-2025. Of the total CO2 emission mitigation, the share of fuel mix effect would be the highest to the total reduction of CO2 emission and then followed by the structural effect. Unlike the fuel mix- and structural-effects, the final demand effect would reduce the CO2 emission at all RPS levels considered (i.e., 5%, 10% and 15%). The share of joint effect is negligible.