When Wes Kennedy started engineering solar systems in the mid-1990s, he pretty much had one integration option: batteries.

At that time, Kennedy designed and installed systems for Jade Mountain, a Colorado-based distributed energy retailer that eventually merged with Real Goods Solar. With very little policy support from utilities, the off-grid market was the dominant driver of business in the U.S. and globally. The vast majority of PV was paired with lead-acid batteries and sold to people who wanted to disconnect from the grid, or who had no other choice for electricity.

That’s the way it was from the 1970s onward for a couple of decades, until a steady march of state-level policies and interconnection laws made tying solar into the grid more attractive. In typical first-mover fashion, California offered some of the first U.S. incentives for solar systems connected to utility wires in 1996. A handful of other states followed, extending net metering to solar and creating state rebate programs.

At that time, Germany and Japan also beefed up promotion laws, creating a strong burst of activity for the grid-tied market globally. In 1997, nearly two-thirds of worldwide solar deployment was off-grid. Three years later, grid-tied installations outpaced off-grid installations globally for the […]