Short answer
A high-temp dishwasher sanitizes with a very hot final rinse, typically 82°C (180°F) or hotter, and usually relies on a booster heater, built in or separate. A low-temp dishwasher sanitizes with a chemical, usually chlorine-based, at a lower water temperature. High-temp uses more energy but no chemical sanitizer; low-temp is simpler to install but needs a steady chemical supply.
High-temp machines leave dishes hot enough to dry quickly, and they avoid chlorine, which can be hard on some metals and finishes. The trade-offs are energy use, the booster heater and more steam, which can mean a hood or a condensate option depending on the machine and your local code.
Low-temp machines run on the building's hot water and rely on a sanitizer pumped in at a set concentration. Dishes come out cooler and dry more slowly, and someone has to keep the chemical containers full and check the concentration with test strips.
Health units generally accept either method when the machine is certified to a commercial sanitation standard and run as the manufacturer specifies. Ask yours how it expects you to verify sanitizing, whether by a temperature log or a concentration log.
Updated · By Norpex