Reasoning:

REDEIA is a regulated infrastructure/utility group with large, stable operating cash flows, but also high leverage and meaningful ongoing capital expenditure needs. The key question is how attractive hybrid bonds are as a financing tool versus straight senior debt, considering both balance-sheet benefit and cost.

At year-end 2022, the company had:

- Equity: EUR 4.894bn
- Noncurrent financial liabilities: EUR 5.544bn
- Current financial liabilities: EUR 1.705bn
- Total financial liabilities: about EUR 7.249bn
- EBITDA proxy: operating profit plus depreciation/amortisation = EUR 961.6m + EUR 545.0m ≈ EUR 1.507bn
- Net debt proxy: financial debt less cash and cash equivalents = EUR 7.249bn - EUR 0.795bn ≈ EUR 6.454bn

That implies net debt/EBITDA of roughly 4.3x, which is elevated but typical for regulated networks. Hybrid bonds could help rating metrics because S&P generally grants partial equity credit, subject to the cap of 15% of adjusted capital.

However, several factors argue against maximizing hybrid use:

1. The company already has substantial equity relative to debt. Equity is nearly EUR 4.9bn, so the balance sheet is not under extreme pressure.
2. Operating cash flow is strong: EUR 1.57bn in 2022, broadly covering capex and dividends better than many leveraged infrastructure peers.
3. Interest rates rose sharply in 2022. The 5–10 year swap curves moved from near-zero/negative in 2021 to around 1.7%–1.9% in 2022. Corporate bond yields and subordinated spreads also rose.
4. Hybrids are materially more expensive than senior debt because of subordination, long maturity/perpetual structure, and call/reset risk.
5. REDEIA paid high dividends, around EUR 544m, so using hybrids aggressively could look like debt-funded shareholder distribution support rather than purely prudent capital structure management.
6. The company already benefited from equity strengthening in 2022, including a large increase in reserves and equity attributable to owners, reducing urgency for maximum hybrid issuance.

On the other hand, using no hybrids would ignore a useful tool for a capital-intensive regulated utility. Some hybrid capacity can efficiently support credit metrics, diversify funding, and preserve rating headroom during a period of high investment and volatile rates.

Therefore, the optimal stance is moderate use, not zero and not near the full S&P cap. A 50% utilization of the S&P hybrid equity-credit cap is appropriate: enough to obtain meaningful rating support and financing flexibility, but not so much that the company overpays for subordinated capital or appears overly dependent on hybrid equity credit.

<answer>50%</answer>