Joint implementation of energy projects can help reduce carbon dioxide emissions by making capital equipment more energy efficient. However, this efficiency can lead to unintended consequences like lower energy prices, which may increase energy consumption. To effectively reduce emissions, international coordination is needed to equalize costs between countries. Focusing on projects in developing countries can lower the overall cost of emission reduction. The impact of improving fuel efficiency depends on the initial emission intensity of the fuel, with the least emission-intensive fuels benefiting the most.