If I remember correctly Taunton has their own municipal power and is like half of what Eversource charges. Massachusetts has like the 4th highest electricity rates at .22 kwh. For most people the payback period at those rates is 4-5 years . I don't think people realize how expensive electricity is in New England compared to the rest of the nation. Here is the data from the EIA.
The Taunton incentive is pretty nuts though at $9k.
https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a