They guarantee it only vs your local utility. Not vs any other ESCOs.
I'm ok with that. I don't actually believe that
any ESCO is cheaper than the local utility, so I'd be good enough with guaranteed savings vs the local utility. Although, I'd like a guaranteed IRR on the amount I'm overpaying every month until the annual refund also, equal to at least the amount I pay on my debt plus a risk factor in case Ambit disappears before paying my refund.
I'd also like to see any ESCO give me a breakdown of their cost vs local utility for my area, for the past year, including all fees. The fact that they won't offer that is in my opinion a bigger red flag than the fact that they're an MLM.
Comcast is my main cable provider, and RCN competes by stuffing mailboxes with flyers with their rates. Meanwhile NSTAR is my main electric provider and all the ESCO's can do is have old acquaintances from yeshiva promise theoretical savings and suggestions that I should become a seller myself.