evidence: Many low-income residents living in National Grid's service area will soon get a big break on their electric bills. The Massachusetts Department of Public Utilities on Monday approved a plan from the company to substantially overhaul its program that gives less affluent residents a discount on their monthly bills. Instead of offering a flat 32% discount to qualifying customers, National Grid will use a tiered structure that gives up to a 71% discount on monthly electric bills. [...] - Now, the first family would get a 71% discount and the second family would still get a 32% discount. Their monthly electric bills would be $58 and $136, respectively.