SEATTLE — Regional power planners say indoor marijuana grow operations in Washington state could need as much electricity over the next two decades equal to what a small Northwest city consumes. Tom Eckman with the Northwest Power and Conservation Council says demand also could grow if Oregon voters pass a ballot initiative in November to legalize recreational pot use. The council has been studying the impacts of electricity needs for indoor pot producing operations since Washington voters legalized recreational pot use in 2012. The council’s analysis says new energy demand among marijuana growers is estimated to grow to as much as 163 megawatts by 2035. That’s about 10 percent of what the city of Seattle uses on average each year.