Accumulated cyclone energy (ACE) is a unit of measurement of the activity of a hurricane season. It is calculated for a storm by taking the storm's wind speed in knots, squaring it, dividing it by 10000, then summing these values for each advisory. The sum of all these values for each storm is the ACE for the entire season. For an Atlantic hurricane season, the average ACE for a full season is estimated to be roughly 92. For the East Pacific, this number is slightly higher.
The most ACE ever recorded in an Atlantic season took place in 1933, which was actually not the most active season on record (2005 was more active, but had less total ACE).