You want the investor's technical advisor to read your economics numbers, agree with them, and make a positive recommendation on your technology to the investor. This usually happens when your techno-economic assessment provides a representative range of possible outcomes, factoring in externalities.
However, after 15 years working with cleantech startups, I see that many early-stage TEAs signal the quite opposite. They quote a single figure for their economic KPI, be it levelised cost, NPV or IRR, or include an arbitrary variation of ±10%, for the commercial plant that has not been built yet.
Yes, as a founder you see the precision - this is what us engineers are geared to do.
But the reviewer sees a team that has not yet located the uncertainty in their technology or business model, and starts widening every number in the model to make up for it. Remember that the investment due diligence is driven by the reviewer's range, not yours
Below are the 3 reasons why a narrow range works against you, what each one costs, and what a range a reviewer believes looks like.
Your spreadsheet is precise, but your estimate is not
A TEA spreadsheet reports your levelised cost to the penny and your IRR to a decimal place. It feels exact because the arithmetic is exact.