Habaneros are small, rounded, lantern- or bell-shaped peppers with a pointed end. Like most peppers, they are green when young, while mature peppers may be yellow, orange, or red. These are small peppers, about 1 to 2 inches (2.5–5cm) in all directions, that give little hint of how much heat they contain. The peppers called Scotch bonnets are closely related, and are sometimes mistaken for habaneros; their heat level is similar.
Habaneros can have heat scores that range anywhere from 100,000 to 300,000 Scoville heat units—or more. How high a chile pepper scores on the heat scale is determined by high-performance liquid chromatography measurement of how many parts per million of capsaicin it contains. This figure is then converted into the historic Scoville heat units that signify how much dilution is necessary to drown out the chile’s heat. The heat level of a chile is given as a range because it varies with how and where the pepper was cultivated.