Around 9% of solar photovoltaic (PV) systems in North America will include attached storage in 2018, says IHS. Growth in storage will be led by commercial systems and IHS expects that 700 megawatts (MW) of PV systems with energy storage will be installed by 2018. That compares with 30 MW in 2014.

“The commercial PV energy storage market in the United States has gained huge momentum in recent months," says Sam Wilkinson, research manager for solar and energy storage for IHS Technology. “Leading suppliers are currently offering highly successful 'no-money-down' sales models to customers, and they have also gained the backing of major investors."

Commercial buildings, which are subject to peak demand charges, can lower their electricity bills by using a battery and PV to reduce peaks in grid power consumption, according to the IHS “Energy Storage in PV Report-2014."

“Incentives, like the Self Generation Incentive Program offered in California, are also making the economics of such systems extremely attractive; but there is no guarantee that electricity tariff structures won't be adjusted, which could affect the economics of existing systems," Wilkinson says.

For residential systems, there is less incentive to install PV systems with attached storage.

Suppliers like STEM and Green Charge Networks are largely driving the growth for energy-storage PV systems. IHS anticipates that Solarcity, a U.S. solar installer, will also be increasingly active in the attached storage market during 2015. Solarcity is already offering Tesla batteries with its PV systems, in order to offer peak demand reduction services.

“Solarcity's third-party ownership business model has enabled it to become the largest residential and commercial solar installer in the United States," Wilkinson says. “The company already has highly established sales channels and financing agreements in place that will make it another major driving force in the commercial PV energy storage market."