Smart windows have been around for a few years, installed on buildings and high-tech airplanes. But complaints abound: they take too long to dim, they don't go fully dark, they're expensive, they become less responsive over time and when they're not dim they tint everything blue.

A new prototype developed at Stanford hopes to solve these problems, per a write-up in the journal Joule.

How they did it: The researchers created a metal ion containing gel that can be applied to windows. When electricity runs through the gel, it changes tint. The current doesn't need to stay on to keep the windows dark.

Why it matters: The researchers estimate that self-dimming windows, when applied to houses, can save 20% in heating costs. They also see applications for electric cars, where less light means less air conditioning, and longer driving times per charge. The technology could also be applied to glasses, to create instant, controllable transition lenses.

Right now these windows are tiny, but Christopher Barile, who worked on the project and is now at the University of Nevada, Reno, tells Axios that they're working on scaling the technology up. "In a few years we hope to have 1 square foot windows," he says. "After that, it's probably beyond the academic realm. The private sector will make them bigger."

It's worth noting that Gentex, the company that makes the dimmable windows on Boeing 787s, is developing a third generation of their technology that they say dims faster and goes darker than the current models.