Over the past few years, the Energy Information Administration (EIA) has continued to add more data about solar power to its reporting. More recently it’s been adding more data about small-scale solar power like rooftop solar and now it’s added data about small-scale solar power to its short-term energy outlook. 

The EIA is defining small-scale solar power as systems under 1 megawatt in size. “EIA estimates that total U.S. small-scale solar capacity was 13 gigawatts (GW) at the end of 2016,” it said. The EIA also anticipated that small-scale solar power will continue to grow quickly. By the end of 2017, they expect it to add 4 more GWs to reach 17 GWs by the end of 2017. By 2018, it will reach 22 GWs.

In terms of megawatt hours those home rooftop systems are expected to generate an average of 39.8 thousand megawatt hours (MWhs) daily—39 percent higher than in 2016. The commercial and industrial small-scale solar is expected to produce 29.7 thousand MWhs daily.  That’s a 21 percent growth rate this year. The systems will produce the most energy in July and least in January. 

Still, measuring small-solar is more challenging than measuring large-scale solar projects. One of the challenges with understanding and measuring how small-scale solar is online is that much of the electricity generated by small‐scale solar PV systems is consumed at the house or business it’s installed at. “So, electric utilities do not necessarily know the total amount of electricity generated by their customers’ solar PV systems,” it stated.

Residential solar is growing the fastest, according to EIA. It estimated that home solar reached about 7.4 GWs at the end of 2016. “Which is 43% higher than a year earlier,” it observed. Commercial and industrial solar reached almost 5.8 GWs at the end 2016. That’s 26 percent higher than it was at the end of 2015. “The July 2017 STEO forecasts installed small‐scale solar PV capacity in the residential and nonresidential sectors will grow to 13,700 MW and 8,200 MW, respectively, by the end of 2018,” it stated.

The office also anticipated strong growth for large-scale solar. At the end of 2016 it totaled almost 22 GWs. By the end of 2018 large-scale solar is expected to rise to 32 GWs. By 2018 then large-scale solar power will reach 1.5 percent of the US’ electric generation capacity. The states that will see the most large-scale solar power are California, Nevada, North Carolina, and Texas, EIA said.