All newly built homes and buildings in California, in the United States, will be required to install a photovoltaic system on the roof from January 2020, a year and a half away. This is what the California Energy Commission decided as part of a broader plan requiring that 50 per cent of the Golden State's energy come from renewable sources by 2030.

A decisive step forward in the energy transition, and one that confirms, once again, the lead taken by the state facing the Pacific Ocean towards a low-CO2 economy, despite the direction set by the federal government. California is currently the largest American market for solar energy and is also one of the most robust markets for electric mobility.

Where the solar revolution in California stands

Criticism has certainly not been lacking. The Bloomberg website reports that this decision could push up the cost of new homes by at least $10,000, while the Energy Commission believes that the new investments in photovoltaic systems will result in only an additional $40 per month for those taking out a mortgage. "Adopting these standards represents a giant step forward," Bob Raymer, an engineer with the California Building Industry Association, told the New York Times.

California is already among the leaders in installed photovoltaic capacity: solar power supplies almost 16 per cent of national electricity and the sector employs more than 86,000 workers. Estimates for the California real estate market project the construction of around 80,000 new homes per year. The new law will increase the number of installed systems and consequently capacity by more than 44 per cent. A further step towards energy production from renewable sources that, it is safe to say, will be followed by other states across the United States.