A study released by the International Energy Agency, The Power of Transformation – Wind, Sun and the Economics of Flexible Power Systems, says that integrating high percentages, up to 30 percent, of variable generation can come at little additional cost in the long term.
Costs depend on how flexible the system currently is and what strategy is adopted to develop system flexibility over the long term. IEA says managing this transition will be more difficult for some countries or power systems than others.
Currently, wind and solar PV account for just about 3 percent of world electricity generation, but a few countries already feature a high percentage. In Italy, Germany, Ireland, Spain, Portugal, and Denmark, wind and solar PV accounted respectively from around 10 to more than 30 percent of electricity generation in 2012 on an annual basis.