solar power techies love PVSelect.com
Solar panels are typically connected to a central grid tie inverter via strings. Multiple solar panels are wired up on a string that goes into the inverter. The number of solar panels that can be wired together on one string depends on the ambient temperatures in the location you are going to install the system, they make and model of the inverter and solar panels being used in the project.
The advantage of using PVSelect.com is that it has 60 different central inverters from 9 different manufacturers and over 200 solar pv panels all within one application, its quite convenient to be able to configure multiple components all from one web application. This is a great tool add to your bookmarks for all you solar techies out there.