By using univariate time series model to eliminate the effect of electricity-saving measures in estimating electricity sales volume of 2012 and 2013, we estimated the imaginary GDP level through time series regression when there were no electricity-saving measures. Assuming that this level of estimated GDP represents the national welfare, we tried to compare this GDP level with the actual realized GDP. Without electricity-saving measures, we estimated using Holt’s*** that annual electricity sales growth rate would have been 2.1%p higher from 2012 to 2013. It is also estimated that annual GDP growth rate would have been 0.7%p higher from 2012 to 2013 without electricity-saving measures. Sufficient power supply that would have covered peak load increase of 2012 and 2013 amounting 2,502MW and 5,247MW respectively would have asked net cost increase around 650.6 billion won, only 2.4% of the loss of national welfare amounting 27 trillion won.