Other forms of power, such as hydroelectric, wind, and solar, are unable to supply base load because the natural forces that power them constantly vary. During 2018, hydroelectric power averaged a 42.8 percent capacity factor, meaning that the nation’s power dams produced only 42.8 percent of their installed nameplate generating capacity on a yearly average; rivers typically flow strongly in spring but dwindle in August. According to the Federal Energy Information Agency (EIA), the figures for wind and solar for that same year were 37.4 percent and 23.6 percent. Wind varies, the sun doesn’t shine at night, and less solar power is produced in heavy overcast. For example, solar PV’s capacity factor in cloudy New England is 13 to 16 percent, meaning that if you install a 1,000-watt solar panel in that region, on a yearly basis it will generate an average of 130 to 160 watts.