HOUSTON, May 9 (Xinhua) -- Electricity generation from solar resources in the United States reached 77 million megawatthours (MWh) in 2017, surpassing annual generation from biomass resources for the first time, the U.S. Energy Information Administration (EIA) said on Wednesday.

According to the EIA, among renewable sources, only hydro and wind generated more electricity in 2017, at 300 million MWh and 254 million MWh, respectively. Biomass generating capacity has remained relatively unchanged recently, while solar generating capacity has consistently risen.

Annual growth in solar generation often lags annual capacity additions because generating capacity tends to be added late in the year.

In 2016, 29 percent of total utility-scale solar generating capacity additions occurred in December, leaving few days for an installed project to contribute to total annual generation. In 2017, December solar additions accounted for 21 percent of the annual total.

Overall, solar technologies operate at lower annual capacity factors and experience more seasonal variation than biomass technologies.

Biomass electricity generation comes from multiple fuel sources, such as wood solids, landfill gas, municipal solid waste, and other biogenic and nonbiogenic materials. The amount of biomass generation these fuels accounted for has remained relatively constant in recent years.

Solar can be divided into three types, solar thermal, large-scale solar photovoltaic (PV), and small-scale solar.

Generation from solar thermal sources has remained relatively flat in recent years, at about 3 million MWh. In 2017, generation from large-scale solar PV systems increased from 15 million MWh in 2014 to 50 million MWh, and that from small-scale PV systems rose from 11 million MWh in 2014 to 24 million MWh. By the end of 2018, the EIA expects an additional 5,067 megawatts of large-scale PV to come online.