MEP stands for Mechanical, Electrical, and Plumbing, the major building systems that make structures functional and comfortable. Mechanical systems include heating, ventilation, and air conditioning (HVAC). Electrical systems provide power distribution, lighting, and communication infrastructure. Plumbing systems deliver water supply and manage drainage and waste. In construction projects, MEP work represents a substantial portion of building costs and complexity. MEP engineers design these systems, and specialized contractors install them. Building permits require MEP plans that meet codes, and inspectors verify installations at various construction stages. MEP systems significantly affect building energy efficiency and operating costs.