By Grant in Blacksburg, VA on 8/25/2008
Just a little more information than I provided previously...
While PV may not make financial sense "today," you are perfectly right that it makes financial sense today to pre-wire for it. But pre-wiring isn't the only preparation you should consider.
The slope and direction of the panels is critical to PV performance. You must also consider the location of chimneys, trees, and other obstructions that can shade the panels.
I have designed my roof and the alignment of my house, so that it will have the ideal slope and direction for PV. Part of this "planning" went into the lot selection as well. By having an ideal roof slope, I have prevented the added future expense of racks to get the proper angle.
I've also decided to spend a little more up front for a 16" standing seam metal roof. This will reduce the cost of adding PV later, because there are PV strips that will adhere to the valleys between the seams. With such a system all roof penetrations can be planned to go under the cap on the ridgeline.
If you are considering "solar" for energy efficiency and cost-savings, I hope you are also looking at solar hot water heaters. They make financial sense to install today.
Without re-typing all of my research on this topic to date, here are links to a thread I started where I am discussing my solar options: