There are two questions that could be asked in terms of understanding market penetration of a residential retrofit program: 1) what is the initial saturation of water conserving devices? and (2) what are the installation and/or retention rates among the households who receive retrofit kits? This paper focusing on the statistical evaluation techniques that could be used to answer the questions. In answer to the first question, a direct survey of households, a residential water audit, a housing stock inventory, and a resale home water audit could be used. A table gives pros and cons of each method. After targeting an area and delivering retrofit kits, the installation and retention rates must be estimated. This can be done using a field survey or telephone survey. Three case studies are offered: two in California and one in Arizona. Problems in measuring retention rates are discussed.