Eversource is legally required to buy evergy on customers' behalf via a process that is designed to minimize energy market price volatility. Energy prices have been high across the board, which is why Eversource had to raise its supply rate.

Some of the alternate suppliers are offering lower rates right now in the hopes you will lock into multi-year contracts and continue paying that rate even when market rates fall below it (at which point you will likely be paying more than Eversource's offer). Although you can switch suppliers any time you want, they are banking on you not noticing when market prices go back down.

So be careful to continue to monitor rates after you switch so that you don't get stuck with a higher rate for years to come.

Here is a pretty good discussion of this: https://ctexaminer.com/2022/12/19/if-youre-thinking-about-leaping-into-the-third-party-electric-market/