Battery storage paired with residential rooftop solar arrays are not a thing of the distant future. It’s happening now and companies like SunPower and SolarCity are already selling package systems.

SolarCity partnered with Tesla to manufacture a lithium-ion battery storage system. In a pilot program, SolarCity is offering the battery setup to California customers for $1,500 down and $15 a month on a 10-year lease agreement.

Currently, the pilot system is only set up to work as a battery backup in case power goes out.

However, SolarCity is working to integrate rooftop solar arrays, battery storage and an advanced home energy management system to work together so system owners could use their smartphones and tablets to monitor energy generation and consumption and dispatch stored power at the most cost-effective times.

At the same time, SunPower has partnered with KB Home to offer an energy storage system to new-home buyers in Southern California.

In its pilot program, SunPower is testing technologies from several different energy storage companies, said Ingrid Eckstrom, SunPower spokeswoman.

These are real projects and they’re just the beginning. Solar paired with storage will become increasingly popular as the cost of batteries drops. Global demand for electric vehicles has put battery research and development into hyper drive. Companies like Tesla are working relentlessly to drive down the cost of high-efficiency batteries.

The electric vehicle manufacturer recently announced finalist cities for its proposed Tesla gigafactory, where it will mass produce batteries for energy storage and electric vehicles.

In addition to rooftop solar systems paired with storage and electric vehicles that demand batteries, utilities are investing in energy storage technologies. California state regulators are requiring that PG&E, Southern California Edison and San Diego Gas & Electric collectively invest in 1.3 gigawatts of energy storage capacity by 2020 in order to stabilize the grid as more and more intermittent renewable energy sources come online.

The growing demand for energy storage that’s destined to drive down prices isn’t just domestic. Germany has a massive initiative aimed at getting home and business owners with solar panels to add energy storage in order to stabilize the grid there now that solar accounts for a sizable amount of the nation’s electricity generation.

All of this investment in energy storage and the actual implementation of mainstream residential solar plus storage packages from two of the largest solar installers in the country should have utilities thinking seriously about how different their futures look from their pasts. Grid defection is a very real threat to utilities.

As most utility companies fight net metering in an effort to slow solar industry growth, progressive utility companies are realizing they will need to rethink their business models if they want a place in the nation’s energy future.