High IRRs often hide fragile assumptions. In volatile markets, attractive returns mean little if projects cannot survive cash stress.
High IRRs dominate solar pitch decks. They are highlighted, underlined, and compared across projects as if they tell the whole story. A 20 percent IRR feels reassuring. A 25 percent IRR feels compelling. In many investment discussions, the number becomes the anchor around which everything else revolves.
This focus is understandable. IRR is familiar. It allows quick comparison. It fits neatly into investment committee frameworks. But in volatile solar markets, IRR often provides comfort without protection.
The core problem is not that IRR is wrong. It is that IRR is incomplete.
IRR assumes reinvestment at the same rate. It assumes smooth cash flows. It compresses timing, volatility, and stress into a single percentage. In stable environments, these simplifications are tolerable. In emerging markets, they are dangerous.
Many high IRR solar projects achieve those numbers by assuming ideal conditions. Payments arrive on time. Currencies move within narrow bands. Downtime is limited. Regulatory conditions remain broadly stable. When these assumptions hold, returns look strong. When they do not, the IRR collapses quickly.
What IRR does not show is fragility.
A project with a high IRR but thin cash buffers can fail faster than a lower IRR project designed for resilience. Payment delays, even short ones, can push the project into liquidity stress. FX erosion can quietly strip real value from nominal returns. Regulatory delays can shift cash flows just enough to break debt service assumptions. None of this is obvious when looking at a single return metric.
Another issue is timing. IRR is highly sensitive to early cash flows. Small changes in the first few years can dramatically inflate or depress the number. This creates incentives to front load assumptions, underestimate ramp up risks, or downplay early disruptions. The result is an attractive headline figure built on optimistic early years.
Investors often discover this only after capital is deployed. The project still generates power. Revenues still accrue. But cash arrives later than expected. Returns stretch out. The IRR that justified the investment becomes irrelevant to the lived experience of holding the asset.
There is also a behavioral dimension. High IRRs reduce scrutiny. When returns look strong, risks feel manageable. Committees spend less time interrogating assumptions and more time debating allocation. In this way, IRR becomes a psychological shield rather than an analytical tool.
Some argue that experienced investors already know this and look beyond IRR. That is true in principle. In practice, IRR still shapes decisions, rankings, and approvals more than most are willing to admit. It is easy to say returns are only part of the story. It is harder to ignore them when capital is scarce and competition is high.
The more useful question is not how high the IRR is, but how sensitive it is. How does it behave under delayed payments. What happens when currency depreciation compounds. How long can the project operate under stress before equity value is impaired. These questions matter far more than whether the base case clears an internal hurdle rate.
Lower IRRs built on conservative assumptions often outperform higher IRRs built on optimism. They survive volatility. They preserve optionality. They give investors room to adapt. Over time, resilience matters more than ambition.
This does not mean investors should accept poor returns. It means returns should be earned, not assumed. In volatile markets, durability is the true source of performance.
High IRRs feel good at approval. Survival feels good over the life of the project. Confusing the two is one of the quiet reasons many solar investments disappoint.
In markets where uncertainty is structural, the most dangerous number in a pitch deck is often the one that looks the most impressive.