The purpose of this article is to analyze the security of supply in Colombia. The analysis considers the Reliability Charge, which is a model adapted in Colombia to guarantee generation investments. We measure the difference among demand supply electricity scenarios. The supply side for new plants takes into account the firm energy obligations; and for on-line plants we perform simulation under different scenarios of the ENSO phenomenon. The demand side was taken for official UPME projections. The simulations show an appropriate size of the reliability charge.