Enel is a very large, capital-intensive utility with stable infrastructure-like assets and recurring operating cash flows, so it can reasonably support some hybrid capital. However, the 2022 balance sheet and market context argue against relying too heavily on hybrids.

Key points:

- Leverage is already high. Total liabilities were €177.5bn against equity of €42.1bn, and borrowings rose materially, with long-term borrowings increasing from €54.5bn to €68.2bn.
- Cash generation weakened: operating cash flow fell from €9.9bn in 2021 to €8.7bn in 2022, while investing cash outflows increased to €13.6bn. Free cash flow before financing was therefore negative.
- Profit attributable to owners fell sharply from €3.2bn to €1.7bn, partly due to discontinued operations losses.
- Existing hybrid equity instruments were already meaningful at about €5.6bn, roughly 13% of total equity and about 19% of equity attributable to owners of the parent. So Enel already uses hybrids as a capital-structure tool.
- The rate environment became much less favorable in 2022. Swap rates rose sharply, and non-financial IG spreads widened. Hybrid bonds would likely be significantly more expensive than in prior years.
- Because hybrids are subordinated and costlier than senior debt, excessive reliance would increase financing cost and could pressure credit metrics, even if hybrids receive partial equity credit from rating agencies.

Overall, Enel should maintain a moderate reliance on hybrid bonds: enough to support credit metrics and preserve balance-sheet flexibility, but not so much that the company becomes dependent on expensive subordinated capital. Among the options, 25% is the most appropriate.

<answer>25%</answer>