The California Energy Commission says the goal is meant to zero-out energy consumption.
The California Rooftop Solar Mandate applies to homes, and complexes up to three stories high.
The size of the solar panel system that's built is based on the square footage of the building, so it can meet the energy usage of the people living in it.
Brandon De Young, of De Young Properties' says California is the first in the nation to create a law like this.
"Energy codes in historical times have only been about the energy efficiency component of the home - so, making sure the home consumes less energy through the year. This new code is - what's very different is the solar aspect. So now they're also requiring a certain amount of solar, which produces energy, right? Two sides of the equation."
The De Young family says for modern day builders, this change shouldn't be too much of a hassle.
And it's one that's good for the homeowner, of course, but also the environment, and the community.
"Of course, the solar companies are loving it, too. They're going to really grow here. And it's great for everyone in the Central Valley, because it'll grow jobs. This is going to be a huge industry now."
The new law should make home ownership more affordable, since homeowners would save on their utility bills.
The Energy Commission says those savings top the corresponding increase in mortgage payments by about $420 a year in total.
De Young says that means people no longer have to sacrifice comfort to save on their bills.
Brandon De Young/'De Young Properties': "This gives you the best of both worlds. Lower energy bill, but still comfortable."
The rules around energy storage devices are also changing.
Those devices now generate a credit toward the minimum building efficiency standard, which will give builders more flexibility in how they meet the state's energy efficiency codes.
There are a few exceptions to the solar mandate -- for instance, if a home is under the shade of trees or other pre-existing buildings, and that makes zeroing out energy consumption impossible, the builders get a break.