Bill payers in Massachusetts could save $500m over the life of 20-year offshore wind power deals thanks to recent federal tax breaks for the sector, said a joint venture of Shell and Ocean Winds planning a major project off the US state.

Mayflower Wind said its winning bid of $77.76/MWh to supply power to Massachusetts utilities National Grid, Eversource, and Unitil from 804MW of offshore wind should drop to $70.26