For years, proponents of natural gas referred to it as a “bridge fuel,” an interim power source on the way to a distant future dominated by renewable energy. That far-off day seemed to pose little immediate threat. Not anymore.

Last year, representatives at the World Gas Conference started referring to natural gas as a “destination fuel” instead, even as one US state after another halted plans for natural gas plants.

The nervousness stems from the plummeting prices of solar panels and battery storage. Natural gas plants are the historical go-to choice for “peaker plants,” which provide electricity during times of highest demand. While rarely used (just a few days per year on average), they’re critical to preventing blackouts.

Now, solar project developers are moving into that territory. Solar developers are bidding prices for new electricity capacity lower than natural gas plants even after adding batteries. In December, Credit Suisse confirmed that utility-scale solar-plus-storage was already cheaper than gas peaker plants in many cases.

After years in the doldrums, US energy-storage installations, mostly lithium-ion batteries, are taking off, having risen 57% to 338 MW in 2018 over the previous year, according to estimates by Wood Mackenzie Power & Renewables. Globally, 6 gigawatt-hours have been installed worldwide.

GE and Siemens have been trying to offload their natural gas turbine businesses as sales tumble. In May 2018, GE cut its sales forecast for its heavy-duty natural gas power plant business by more than half, saying demand would stay at the reduced level through 2020.