This paper evaluates the manufacturing cost reduction factors for a PV system achieved in recent years. First, it is seen that technological development has greatly accelerated system cost reduction. In order to further reduce costs, it is important to develop tandem technologies to improve efficiency. Secondly, by comparing the cost structure in 2012 and 2015, a reduction in manufacturing cost is observed due to improvement in manufacturing technology. Thirdly, by comparing with the PV cost analysis of 1991, this methodology is proven to be able to estimate future technical levels. This paper thus proposes the methodology of technology assessment using quantitative technology scenarios.