Well, I found part of the answer.... Cost of Capital is set under General Settings-->System Options.
On the NPV calculation, here's a real simple example:
* Project cost - $5,000
* Project benefit - $10,000
* Cost of capital - 10%
Let's say I sink my cost in Year 1 (planned cost starts 1/1/2010 and ends 12/31/2010). Benefit begins Year 2 when the project ends (planned benefit starts 1/1/2011 and ends 12/31/2011).
Have all the Clarity parameters there, right?
Plugging these into Excel, the NPV function in Excel says my NPV is $4,091 (that is, $9,091.91 - $5,000.00 = $4,091.00)
Plugging these into Clarity, the NPV comes out to $3,840.91, a difference of $200.
Just rounding error here? Or am I missing something? The larger, and more time-spanning I make the projects, the wider the difference in NPV between Excel and Clarity...
Thanks!