An example that is almost right on your numbers (600 kWh, $179 last winter, $293 this winter) was given back when they warned everyone in September: https://www.nbcboston.com/news/local/some-massachusetts-customers-will-see-a-64-increase-in-their-electric-bills-this-winter/2840633/

It also said the delivery rate remained flat, which is why your entire bill did not triple.