You might be wondering why the headline to this month’s Sun Dial column is a popular song lyric. There are two reasons: 1) John Lennon and the Beatles were awesome, and 2) like Mr. Lennon, I want to ask you to imagine something.

Imagine a country where solar is on every rooftop. Is that so impossible? Could that nation be the U.S.?

In our May 2016 issue, we highlighted a study from the National Renewable Energy Laboratory (NREL) finding that if all solar-ready roof areas in the U.S. actually featured PV installations, the resultant energy would provide an astounding 39% of the entire country’s power needs.

Imagine what effect that would have on our climate, let alone our energy bills. And it appears the NREL figure covers only existing roofs that are “suitable” for solar, which typically means they should have the proper angle and unshaded area and be strong enough to support the weight of a system.

How do we get installations on all of those existing rooftops, and how could we ensure more are solar-ready in the future? Certainly, solar companies and other stakeholders are doing their part and getting as many consumers on board with renewables as they can; however, California requires most new small and midsize buildings to be solar-ready, and a handful of progressive cities in The Golden State are going even further - mandating rooftop solar.

On April 20, San Francisco became the first major U.S. city to require solar installations on new residential and commercial buildings constructed in its city. As Supervisor Scott Wiener, author of the newly passed ordinance, explains in an announcement, the existing California law requires that a certain amount of rooftop space on all new buildings up to 10 stories tall be primed for solar. Wiener says his new ordinance simply builds on that requirement, calling for solar to actually be installed on that solar-ready rooftop space starting in 2017.

However, San Fran isn’t the only city with a rooftop solar requirement; smaller municipalities are also in the club. Santa Monica passed a solar ordinance in May, and that rule, similarly applying to new residential and commercial buildings, was slated to go into effect by the time you’re reading this. The city government says the cost-benefit ratio for the necessary solar installations “is strong.”

Back in 2013, the cities of Lancaster and Sebastopol helped lead the way on such mandates: Technically, Lancaster was the first city in the U.S. to require solar on new homes, and Sebastopol quickly followed suit by establishing a requirement for both new homes and new commercial buildings.

I spoke with Councilman Patrick Slayter, co-author of Sebastopol’s solar rule, right after the city council passed its ordinance. “It just seems like the right thing to do,” he said. “Having rooftop space available, with unencumbered solar access essentially from sunrise to sunset, but not considering having a PV array on it - that just seems unconscionable to me.”

Three years later, I caught back up with Slayter, and he tells me the ordinance has been a success so far. According to him, the city has added about 300 kW of installed solar since we last spoke, reaching almost 1.5 MW. That might not seem like a lot to many, but in a small city of 7,500 people and 2,100 dwellings, it’s nothing to scoff at.

Regarding San Francisco’s and Santa Monica’s new ordinances, he says, “I am not surprised that other communities are jumping on the solar wagon.”

OK, OK: I admit it - A country with solar on every single rooftop is likely never going to happen. Nonetheless, the cities of Lancaster and Sebastopol made their solar dreams a reality, and so, too, will San Francisco and Santa Monica. Perhaps every city and state in the U.S. could at least try to join in. Imagine that.