Solar Irradiance for PV Systems

The solar irradiance shown on the location/resource page for the area of a prospective customer is 3.81. I know that changes with tilt. How can I find what value is actually being used in calculations after the tilt has been set? I think it should be near 4.2.
The value you see on the Location and Resource page for global horizontal irradiance is the sum of the hourly data from the weather file and is in kWh/m2/day. After you run simulations, you can calculate the global incident irradiance in kWh/m2/day as follows:

1. 
   Click Data, and under Single Values, check Annual POA total radiation after shading and soiling (kWh). You'll need to scroll down to find that variable. That value is in kWh/year.
2. 
   Take that value, and divide it by the Total module area in m2 shown on the System Design page. Now you have a value in kWh/m2/year.
3. 
   Divide that value by 365 days/year to get the irradiance in kWh/m2/day.

Best regards,

Paul.