Carroll County resident Pat Costner walks under her three solar arrays this warm autumn afternoon to a shed where she keeps a collection of heavy-duty batteries.
“They’re fully charged right now,” she says, gesturing at the noontime sun above our heads.
The retired Greenpeace senior scientist operates a grid-tied solar energy system with an unusual electrical utility meter.
“It tells me if I am buying or selling,” she says. “Today is a selling day.”