U.S. utilities could save $9 billion per year in grid upgrades and residential customers could cut their electricity bills by 40% if utilities adopted demand-flexible rate plans, according to new research by the Snowmass, Colorado-based Rocky Mountain Institute.

“The study looks at demand flexibility—the ability to shift energy usage across the day based on price signals,” Greentech reports. “Adopting a conservative approach, RMI looked only at residential air conditioning, domestic hot water heaters, clothes dryer timers, and timed electric-vehicle charging.”

RMI uncovered a huge business opportunity by assessing rate structures like real-time pricing, demand charges, and compensating users for the costs utilities can avoid by buying distributed solar. “More than 65 million Americans already have access to some form of time-of-use rates,” Tweed writes. “The report identified the investment opportunity as more than $900 million for vendors that could help customers unlock those savings.”

She draws a parallel between demand flexibility for residential customers and battery storage for commercial uses. “Just as battery storage offerings are sold to commercial customers as a way for them to control bills and increase resiliency, demand flexibility would be offered to residential customers so they wouldn’t even notice when their grid-connected assets, like smart water heaters, are offering grid services and flattening load.”