The number of customers like the Borkowskis is growing, but small. Still, they are beginning to reveal the outlines of a new energy future, where an increasing number of customers would no longer be merely using a utility's electricity but helping to supply it, potentially allowing them to move off the grid entirely.

For utilities, the seismic question is how to respond. Some are trying to slow down the transition, seeing in the rise of solar panels on the roofs of homes and businesses an existential threat. But here in Vermont, Green Mountain is attempting to carve out a more proactivevision of the future where the line between customer and power provider blurs by mutual consent.

"We are trying to accelerate the adoption of disruption," says Mary Powell, the utility's president and chief executive officer.

In recent years, that disruption has been accelerating all on its own. Historically, utilities have built large power plants and distribution facilities and delivered electricity to customers. But a range of new energy technologies has naturally led homes and businesses toward becoming mini generating stations, says James Mandell, an analyst with the Rocky Mountain Institute, a renewable-energy think tank in Snowmass, Colo.

"People are buying smart appliances, like a Nest thermostat, because they like them. They lower their costs and add convenience," Dr. Mandell says. "Increasingly, we're going to see customers want a battery [backup for homes] because it improves the power quality and protects them from outages. We've already seen customers wanting solar for a lot of the same reasons. If you combine solar, batteries, and some of these smart controls, you have customers that can supply a lot of their own needs."

As a result, many customers large and small will draw less electricity from large power plants - facilities utilities have paid a lot of money to build and operate. By 2020, the falling costs of panels and related installation expenses are expected to bring the price of solar energy "to within striking distance" of new construction for tradition fossil-fuel plants and for nuclear plants, according to an analysis by researchers with McKinsey & Company, a global management consulting firm.