While only 4 megawatts (MW) of solar photovoltaic (PV) + energy storage capacity was deployed in the US in 2014, significant change is coming to the sector, according to GTM Research. Altogether, less than 0.1% of all solar PV installations in 2014 were accompanied by energy storage systems. Amazingly, this is actually a decrease in installation rates over earlier years.

As predicted by GTM Research, though, things are changing this year. According to the research firm, 22 MW of solar + storage will be deployed in total in the US by the end of 2015; by 2020, the firm’s prediction is that the total will be 769 MW.

The largest solar + storage market in the US is predicted to be California (with 422 MW of capacity) — unsurprising, as California is currently the largest solar + storage market in the US and also the largest solar market, by far.

With regard to monetary figures, the market is expected to surge to $246 million in 2015, then to $643 million in 2016, and then to $3.1 billion by 2020.

Here’s some more via GTM Research:

There are a number of drivers for the increased level of industry and customer interest. Several technologies, led by lithium-ion, continue along rapid commercialization paths, bringing down costs and providing one of the biggest drivers for the industry. Along with cost reductions, solar-plus-storage value streams continue to advance from traditional backup to multiple use cases. These benefits vary in three ways: frequency of use, discharge duration, and the key beneficiary.

Generally speaking, benefits that have more frequent use improve the overall economics of the system. These benefits are not necessarily mutually exclusive, although there are limitations based on technology, availability of charge, frequency and timing of multiple applications. Apart from the technical constraints, front-of-meter benefits have generally not been monetized, except in a few markets at pilot scale.

Market rules and policies are still evolving in reaction to the proliferation of distributed energy resources. But across the major state markets with attractive incentive landscapes, the value proposition of solar-plus-storage varies by customer segment. The use cases can range from homeowners optimizing rooftop solar compensation in response to net energy metering reforms and time-of-use retail rates to peak demand shaving for commercial customers.

With significant changes coming to the country’s electricity markets as a whole, the solar + storage sector remains one that’s really worth keeping a close eye on.