There are other factors to consider in this and that is the weather. The guy is in Sunnyvale, CA -- they get far more weather there and have more frequent cloudy days than here in Phoenix,AZ. Therefore, put the $38,000 solar investment to use in Arizona that has an average of 360 days of sunshine per year and longer days with the sun in both summer and winter than Sunnyvale, CA.
In addition to the sunshine per year, there's the cost of the electric provider from the utility that should be taken into account. PG&E rates differ from other utility companies such as APS or SRP here in Arizona. Therefore, if SRP or APS charges more than my savings per year would be higher just because of higher rates.
The only way that one can compare one solar installation to another is to have one compared to another solar installation of similar, if not exact, size and geographical location. It would not surprise me to know that a smaller installation in Phoenix can generate the same amount of electricity daily than one in Northern California simply due to the longer days.