I just tried to google electricity by source in the U.S. Seem the Energy Information Administration site is down.
https://www.eia.gov/energyexplained/index.cfm?page=electricity_in_the_united_states
But this WaPo article has a very good interactive graphic just a little way down that allows you to click on the energy source and the graph recompiles by state.
The majority of electricity produced in MA is by natural gas, a little surprised by that. Coal is 6%
https://www.washingtonpost.com/graphics/national/power-plants/?utm_term=.90b267c24baf
Great stats as you scroll down.
Natural gas, coal and nuclear make up the vast majority of our electricity production.