Incorporating energy from renewableresources into power system planning is an important issue.As countries generate more energy from renewable sources,that energy must become part of the power-system planningprocess. In 2004, investments in all forms of clean energyrepresented about 20 percent of total global investment ingeneration capacity. By 2011, that share had topped 40percent. This paper explains the various reasons behind thepush for renewable sources, chief among them being reducingclimate-altering emissions. The paper answers the followingquestions giving a brief synopsis of each: What is the keychallenge? What solutions are available? What are the keylessons learned. A few case studies are also used throughoutto illustrate key points.