Average wholesale electricity prices at major trading hubs across the United States during the first quarter of 2016 were significantly lower than during the same period in 2015, ranging from 24% lower in California to 64% lower in New England. Monthly wholesale prices for the rest of 2016 were slightly below 2015 prices and generally averaged between $20 and $45 per megawatthour (MWh). The primary driver of the low wholesale electricity prices was the sustained low cost of natural gas, which is the fuel that often determines the marginal generation cost in most power markets. The low cost of natural gas also encouraged increased use of the fuel for U.S. power generation in 2016.
Source: Wholesale power prices in 2016 fell, reflecting lower natural gas prices – Today in Energy – U.S. Energy Information Administration (EIA)