Right now in America, there are about 2 million homes with solar panels. Considering there are about 90 million single-family homes, that doesn’t seem like a lot. But consider this: we’re now on track to start adding a million new solar-powered systems each year. It’s taken a while to get here, but solar is increasingly becoming a popular option to power the Home of the Future.

The number of homes with solar “will tick up pretty quickly,” says Justin Baca, vice president of markets and research for Solar Energies Industries Association. The panels are growing cheaper, growth is happening at double-digit rates each year, and some key policymakers are becoming enthusiastic: California recently passed a requirement that new homes include solar panels.

“We’re personally looking forward to a day when solar is as ubiquitous as AC.”

Of course, not every state is as weather-fortunate as California, but various solar companies point out that they’re starting to expand beyond the Golden State and Florida. Anne Hoskins, chief policy officer of Sunrun, the nation’s largest residential solar installation company, says the company is growing in states like Wisconsin and Illinois. Vivint Solar CEO David Bywater says that his company has a lot of solar customers in New England. Baca notes that Maryland and the Carolinas are starting to have more solar panels, and New Hampshire and Vermont have quite a bit when you take the size of the states into account.

Most homes with solar panels are still connected to the traditional electric grid. Cloudy days (and eclipses) will happen, and that’s when it’s helpful to still be connected. Typically, when the system is producing more energy than needed, they export to the grid. And when they produce less, they take from the grid. Costs are based on consumption, says Baca. You’re not supposed to export a lot more than you consume, so the systems tend to be designed to be a bit smaller than what is needed for 100 percent. (Typically, they’ll target 80 to 90 percent power from solar.)

But that doesn’t mean that being 100 percent off the grid isn’t possible, says Bywater. Energy storage is key when it comes to renewables at any scale; you want to have a backup. There are a few different ways to store energy, but the kind that is most helpful for the home is to use a lithium-ion battery — similar to the one in your phone but much, much larger. These can plug into the solar panel system and store up energy during the sunny days. Then, they kick in when the clouds pass over.

Though solar power is cheaper and becoming increasingly popular, the industry is facing a few obstacles. The permit and inspection regimes are fragmented, explains Baca. Different jurisdictions and local governments have different versions of the building code, and they’re all interpreting them differently. “That makes for a very fragmented and inconsistent process that makes it burdensome for companies to install solar,” he says. For example, they could sell to a homeowner who is excited about getting the panels. But the permitting process takes three months, and then the customer gets frustrated and cancels. So even though California’s legislation was a win for the solar industry, it might be the outlier. Policy is still a bottleneck.

If solar becomes ubiquitous, we’ll likely see it being integrated with smart energy management systems in the home, predicts Bywater. These will regulate the battery, the home by using different sensors, and the solar panels. “The real trick is for the system to know how to make someone comfortable and how to be aggressive on conserving energy,” he says. It should know the optimal temperature of the home and how to change it based on utility rates and the time of day to save money.

Ultimately, says Baca, “we’re personally looking forward to a day when solar is as ubiquitous as AC.” Very few places had air conditioners when the technology first became available, and now it’s rare to find a builder who would create a new home without it. “People think something’s missing when it’s not there,” he says. “I think that’s where we’re going with solar, and I hope we see it sooner rather than later.”