If we saw a dc customer approaching their power limit we would typically have a conversation or message them to make sure they were aware. If they anticipated needing more sustained power we would update their agreement accordingly.  Sometimes it would be a one-time occurrence so we would typically let it slide.  If they needed additional power usually it was in 10 Amps per cabinet or 5-10kW increments if in a larger footprint (cage or suite).  We typically did not punish our customers for overages because we wanted them to continue to grow with us and we had the additional power capacity available.  Some colo providers will put a premium on power overages 5-50% (I have seen all over the board) in order to make additional revenue on power spikes, make the customer more accountable to staying within their power commit or maybe the power is limited at that dc or on that floor.  Hope this helps. Feel free to call with additional questions - 816-213-7731.

Greg