Blessed to be in the PNW it seems!
Like others, our experience here (3 marinas in the last 20 years) is we are charged a very small monthly access fee to use our marina dock AC (currently $10 a month I think) and then assessed a KW/hr charge for our actual usage. (One marina in the past charged us if we went over a small nominal monthly use. Currently we pay any use.) We typically heat with resistance and dehumidify in winter and don't have air conditioning in summer. So like GFC, pretty small in summer, higher in winter when we have a dehumidifier and a little heat running. I'd have to check with the Admiral for sure, but I don't think our monthly electric bill ever gets more than $35 or $40 in the winter, and closer to $10 or $15 in summer.
Our first marina here was a county run port marina in La Conner, the second a privately owned/run marina in Anacortes, and now we are in a privately owned marina owned by an HOA of sorts in La Conner.
Might be the norm in the PNW for power based on our historical abundance of cheap power?
I feel for you with the communication and lack of empathy from your marina. Again I feel blessed; we have a pretty dang good marina when it comes to things like this. Even when we've "violated" the rules by putting our little runabout in our slip without getting prior authorization/permission, we got a phone call from the dock master first to clarify and inform rather than negative action. I think we are super lucky because our marina exists to serve the private homeowners in the community where it exists, so customer service is relatively high on its list of priorities. We're on a first name basis with the dock master and the office administrator for the marina. Because of the HOA-type public entity organization of our marina, any major policy changes are discussed in advance by presentation to a board of directors - if they decide to make a change they require some publication in advance of the change. We end up seeing it both in board meeting notice/minutes and then later in communications from the marina. However, that should be the NORM for any business with a tenant type customer base, marina or otherwise. Unfortunately not all fall into the business practice or situation we are in, and not all fall into the economic or other situations we find ourselves in in our part of the PNW, so other marinas might make other business decisions that have negative effects like you've seen here.