How is CFE billing solar clients as far as KWHs produced and used?

I produce more KWHs( kilowatt hours) then I use but but I'm being billed for hours not used. Can anyone explain this to me please.

There is a minimum charge, which you pay regardless of KWH usage.

And at one time and I believe, still today that the minimum charge is for 30 KWH per month whether you use any of those 30 kilowatt hours or none of those kilowatt hours.

I have two more panels than I need. And I almost always generate 30 to 80 KWH more than I need each billing period. And I am building up a bank account of extra KW hours. But I still pay the minimum charge which is the equivalent of 30 KW hours per month, which is no big deal. I was billed and paid about 23 pesos per month or now that I am billed every two months, 46 pesos per billing period.

And my experience is exactly the same as Pete's. I got annoyed having to go and pay 46 pesos every two months, so I went in to Chapala and fed the machine 500 pesos last January... and my bill is always a big fat zero now and I just file it.
I know how much I produce because it is tracked on the internet and I also keep track, on a calendar once a week, the difference between sent and used on the digital meter. I currently have 431 kwh in the bank to use my electric heater in the bedroom when it gets cold. Not bad for only 5 panels!