In February 2013, California energy officials sat down with power-industry executives to figure out how to avert an approaching calamity: The rapid rollout of wind and solar electricity was stressing the state’s grid. The more renewable energy California added, the more its power supply could be whipsawed by a cloudy day or a windy storm. Some at the meeting warned that problems, such as rolling brownouts, could start to show up later that year.

Those same worries were being echoed from Hawaii to Florida, as authorities struggled to load aging electricity grids with ever-greater amounts of renewable power. At the time, renewable energy accounted for about 14% of California’s electricity output.

Today, California often gets as much as 30% of its power from renewables; there are periods of the day when production can soar to 40%. California legislators just approved a plan that would require half of all power to come from renewables by 2030. Still, the tipping point the power industry feared hasn’t materialized.

The experience of California and other states with high concentrations of solar and wind, such as Hawaii, is challenging long-held assumptions about the limits of renewable energy. As the boundary of what is considered possible expands, so does the momentum around investment in new technology and resources.

“You’ll hear numbers [that] people bandy about and most of them are wrong: ‘We know we can get to at least 35% or 40%,’ ” says Haresh Kamath, an expert in energy storage and distributed generation with the Electric Power Research Institute in Palo Alto, Calif. “Now that we’re getting to those numbers, people are pushing them up again.”