The heat of peppers is measured using the Scoville Heat Scale, which ranks the heat of a given pepper in units known as Scoville Heat Units (SHU). Bell peppers of all colors register zero SHU, meaning they're not hot at all. Jalapeños are medium, measuring 2,500 to 8,000 SHU, while extremely hot chiles like habaneros or Scotch bonnets come in at 100,000 to 350,000 SHU.