The distribution engineer told me the design engineer would require it, and that I should ask my engineer what it would cost.
If they are requiring me to have a filter that isn't specifically required in code then they should be able to provide me an example of what I would need to buy. I'm not interested in paying an engineer to bounce proposals back and forth to see what sticks.
Because of the service size I will need to hire an engineer with a stamp to write down on a piece of paper the number of circuits and miners on each circuit. Load factor, power factor, etc. My electrician has one that will help on the simple job, but I told the poco I didn't want to waste any money until everything was basically approved and the costs known.
Like I said, the distribution engineer has been very helpful. After explaining the situation to him, like the economics of mining with .1415/kw electricity, he is agreeing to basically jump forward and price the system and follow up with the engineering later. I should hear back about the filter Monday or Tuesday next week. I am going to see if the power factor is good enough on the power supplies that they will forget about the filter.