The June 5, 1975 NASA JPL Goldstone Demonstration of high power long distance wireless power transmission successfully transmitted 34kw of electrical power a distance of 1.5km at an efficiency of greater than 82%. At the time, it was the world record for high power long distance wireless power transmission.
Citizens for Space Based Solar Power 
I am organizing a workshop on the state of the art in microwave power transmission for the IMS conference in Anaheim CA 2010. Anyone able to participate and give a retrosective of the NASA work or be willing to brief on more recent work?
Let me know by 5:30 PM (EDST)14 October, 2009