This paper presents two methods, namely those using noise and homogeneity measurements of a large area solar cells, for determining the local defects, which bring down efficiency and long reliability of single-crystal silicon solar cells. As a result of the non-uniformities (non-homogeneity) in the large junction area, local areas with lower built-in potentials at the junction lead to hot spots and reduced reliability. The two techniques can be used to give a precise description of the quality of the product technology. Correlations between noise and inhomogeneities for an ensemble of 30 silicon solar cell samples are given.