Eversource doesn’t keep the money on the supply side. They purchase electricity on your behalf for whatever the market rate is. They lock the price in for 6 months and whatever you use is x that rate. You pay your bill and Eversource turns around and gives that money to whatever company produced that energy.

If you change your supplier, Eversource still collects the money, but it just passes through them and goes to the company who actually produced that energy.

It won’t affect Eversource if everyone stopped using them as a supplier since they do not produce energy. You shouldn’t just lock in a price for 3 years and not check it again. Every 6 months, the rate changes. So, Eversource could be cheaper in June again. But, you run the risk that in January 2024, it will go up higher, and you’ve now gotten out of a better, overall long-term price, with an alternative supplier.