It really depends on the heat level of the chiles you use. Hatch green chiles range from relatively mild to pretty hot. Luckily they are usually labeled as such at the store so you know what you're getting into. Be sure to pick a pepper that suits your personal preference. If you use canned chiles then it should say how hot they on right on the label. I typically use quite a hot chile and while the mac and cheese definitely have a solid kick, it doesn't burn your head off.