Best in class electrical contractors are bringing 20-30% of their field labor hours into the prefabrication shop at an average productivity improvement of 30%. Unfortunately for union electrical contractors, many of the firms having the most success with scalable prefabrication are merit shop electrical contractors. Merit shops are achieving great success by implementing lean manufacturing principles in their prefabrication shops. Contractors must stop thinking about prefabrication like a contractor and start thinking about it like a manufacturer. We will discuss best practices being deployed in the industry including photos of the most productive and progressive shops in the US, the importance of product standardization, linking estimating to detailing to prefabrication to field installation, and logistics and inventory management ideas to further enhance cost reductions resulting in higher margins.