Nuclear power plant steam generator replacement decisions involve roughly $1 B in capital and replacement power costs. SDG has been engaged in helping utilities make this type of decision for the past 20 years. For PG&E, we decided to change our analytic approach to include a Monte Carlo simulation. This paper discusses the results and the strengths and limitations of this analytic approach. Before this case, a California utility decision of this size had never included a Monte Carlo simulation. In contrast, another utility in California filed for steam generator replacement using a base case approach and has had very different results.