In the future, our quality of life will be determined by the quality of our cities.

We need buildings in which to live, but crafting those buildings is making it harder to live on this planet. As much as 10% of global carbon emissions come from the production of concrete. One ton of CO2 is generated by making one ton of cement, which is made from limestone and a few other things heated to an extremely high temperature.

But what if concrete could generate its own energy? The era of photovoltaic concrete may be getting closer. Photovoltaics, which work by converting light to energy via semiconducting, are starting to migrate from solar panels into the building materials themselves.

In November 2017, Swiss firm LafargeHolcim—the world’s largest cement maker—and Heliatek, a German solar-panels company, debuted photovoltaic concrete panels at French construction fair Batimat, according to Architizer. These panels are concrete with built-in ultra-think solar panels that can be delivered as is on site. The companies say that a typical 10-story commercial building covered in 60% of these panels would generate about 30% of its annual energy requirement.

Researchers from ETH Zurich university have also developed their own ultra-thin, sinuous material in which layers of heating coils and solar cells are built into the layers of concrete.

This technology is notoriously complicated. In 2016, Tesla debuted photovoltaic solar-roof tiles that looked better than the regular tiles that sit on the roofs of most American houses. But more than two years later, very few of them have actually been installed, partially due to complications with the manufacture and also reportedly due to the “aesthetic concerns” of Elon Musk. The company has now promised a large-scale rollout of the tiles in 2019.

Getting photovoltaic concrete ready for actual commercial building work will probably be no easier.