This paper estimate the $CO_2$ reduction potential that can be achieved by improving the technical efficiency of input factors in the manufacturing sector. Technical efficiency in each manufacturing firm was estimated using the DEA technique. Depending on the returns-to-scale assumption selected, average technical efficiency was estimated to be between 0.467 and 0.643. These estimates suggest that, when the efficiency of electricity consumption in the manufacturing sector is improved, the overall $CO_2$ emissions can be reduced by 17.1-25.5%. Recently, the Korean government has adopted a low-carbon-green-growth policy with the goal of reducing greenhouse gas emissions by 30% below the BAU level by year 2020. The analysis of the paper suggests that this goal can be achieved through improved efficiency of electricity consumption.