This paper presents a comprehensive overview of the life cycle GHG emissions from wind and hydro power generation, based on relevant published studies. Comparisons with conventional fossil, nuclear and other renewable generation systems are also presented, in order to put the GHG emissions of wind and hydro power in perspective. Studies on GHG emissions from wind and hydro power show large variations in GHG emissions, varying from 0.2 to 152Â g CO2-equivalents per kWÂ h. The main parameters affecting GHG emissions are also discussed in this article, in relation to these variations. The wide ranging results indicate a need for stricter standardised rules and requirements for life-cycle assessments (LCAs), in order to differentiate between variations due to methodological disparities and those due to real differences in performance of the plants. Since LCAs are resource- and time-intensive, development of generic GHG results for each technology could be an alternative to developing specific data for each plant. This would require the definition of typical parameters for each technology, for example a typical capacity factor for wind power. Such generic data would be useful in documenting GHG emissions from electricity generation for electricity trading purposes.