Last summer, I was playing Frisbee at a sports field that's adjacent to Paine Field (Everett) when I noticed an unusual aircraft flying overhead - basically looked like a powered sailplane, but no discernable engine noise, just a drone like hum. It circled around the area for perhaps half an hour before leaving. Reasonable sure it was an electric aircraft - probably doing some testing. Staying close to the airport meant that if something went wrong it could easily glide in for a dead stick at the airport.
Sort of an intriguing idea - an electric sailplane that could takeoff on it's own power, find a good area of thermals and shutdown the electric motor and glide for a while, then return to the airport using the electric motor if necessary to extend the range.