We present a model for analyzing how gradual implementation of distributed generation (DG) in a grid can mitigate carbon dioxide emissions of a utility company. Our model uses the grid parameters and publically available data on the electricity supply and demand of a power company in Northern California: Sacramento Municipal Utility District (SMUD), whose main central power plant uses natural gas. Setting the target year at 2050, our model uses a logistic function for forecasting the SMUD's electricity supply and demand. We then use PowerWorld software and calculate the reduction in line losses based on the size and location of distributed generators on the grid. And finally our model determines the carbon dioxide emissions for various scenarios with business-as-usual as well as with renewable distributed generators gradually (annually) brought on line.Our results show that under business as usual scenario, SMUD's carbon dioxide emissions will rise from its 2010-level of 2.2 million metric tons to 2.888 million metric tons; an increase of 31% over four decades. However, by implementing a modest 40 MW of renewable DG every year, SMUD can lower its carbon dioxide emission to 0.83 million metric tons in 2050, which is 62% lower than its 2010-level emissions. This significant reduction in carbon dioxide emission is due to both line loss reduction and the implementation of renewable distributed generation.