This report summarises recent findings on wind integration from the 15 countries participating in the International Energy Agency (IEA) Wind collaboration research Task 25 from 2012–2014. Both real experience and studies are reported. The national case studies address several impacts of wind power on electric power systems. In this report, they are grouped under long-term planning issues and short-term operational impacts. Long-term planning issues include grid planning and capacity adequacy. Short-term operational impacts include reliability, stability, reserves, and maximising the value of wind in operational timescales (balancing related issues). The first section presents the variability and uncertainty of power system-wide wind power, and the last section presents recent wind integration studies for higher shares of wind power. Appendix provides a summary of ongoing research in the national projects contributing to Task 25 from 2015–2017.@en