China has embarked on a massive program of low-carbon electricity (LE) deployment, in order to reduce its current dependence on coal. The cumulative installed capacity of LE in 2015 was almost four times of that in 2002. Moreover, China has a target of 20% for non-fossil fuels in primary energy consumption by 2030. LE provides substantial carbon savings in the use phase, but LE infrastructure tends to require more materials than their fossil-fuel electricity counterpart. Here we estimate the carbon 'overhead' from infrastructure expansion during China's transition to LE. We report estimates of the learning curves of the carbon intensity of LE installation, calculated from regional historical data in the period 2002-2012. We combine this information with the predicted cumulative installed capacity from well-known scenarios from national and international bodies. We then project the trends of carbon impacts from LE investments up to 2040. Our results show that, under all scenarios and every year, the annual carbon impact of LE investments never exceeds 4% of China's total carbon emissions, and that the carbon impacts of the expansion in LE infrastructure show either a steady decline or a peak during 2030-2035 before declining further.