For non-financial readers looking to understand Internal Rate of Return (IRR), which I used as the foundation for Energy Internal Rate of Return (EIRR) in my article Managing the Peak Fossil Fuel Transition, you can find a good discussion of IRR on Wikipedia.
In practical terms, IRR is nearly always calculated in a spreadsheet from a column of numbers indicating the directional cash flows (negative for investment, positive for returns.)
The Excel spreadsheet I used to estimate the IRRs of various generation technologies is available here.
Tom Konrad
