Let's work through the reasoning step by step.

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### 1. Understanding S&P’s hybrid limit
S&P Global Ratings caps the equity credit from hybrid bonds at **15% of total adjusted capital** (total adjusted capital = total debt + equity).  
The question is to what extent should ENEL utilize that cap — 0%, 25%, 50%, 75%, or 100%.

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### 2. ENEL’s equity and hybrid data
From the facts:

- **2023-01-01 total equity**: €42,082 million  
- **2023-01-01 equity attributable to owners of parent**: €28,657 million  
- **Perpetual hybrid bonds (equity component)**: €5,567 million at end of 2022, same as at end of 2021 (no new issuance in 2022).

Hybrid bonds are part of equity under IFRS but treated separately by rating agencies for adjusted capital.

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### 3. Total adjusted capital
We need total debt + total equity.

**Total debt (short + long):**
- Long-term borrowings: €68,191M  
- Short-term borrowings: €18,392M  
- Current portion of long-term borrowings: €2,835M  

**Sum of borrowings**:  
68,191 + 18,392 + 2,835 = €89,418M  

**Total equity**: €42,082M  

**Total adjusted capital (debt + equity)**:  
89,418 + 42,082 = **€131,500M**

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### 4. Maximum hybrid allowed for 100% of S&P cap
15% of €131,500M = **€19,725M**.

ENEL currently has €5,567M in hybrids.

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### 5. Situation assessment
ENEL’s hybrid amount is far below the cap:
- Current usage = €5,567M / €19,725M ≈ **28% of the cap**.

So, at present, they are well within the limit and could increase hybrid usage significantly before hitting the cap.

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### 6. Strategic considerations
- Hybrids are **equity-like** for rating agencies but **tax-deductible** like debt in many jurisdictions.  
- For a capital-intensive utility like ENEL, using hybrids can support credit metrics while lowering after-tax cost of capital.  
- Given rising rates in 2022 (swap curves rose significantly), hybrid issuance may be more expensive than in 2020–2021, but still cheaper than pure equity.  
- ENEL has a large investment program, meaning they need to optimize funding.  
- Given their current low utilization, it would be reasonable to increase toward the **100% cap** to maximize rating agency equity credit.

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### 7. Final decision
A full **100%** usage of the hybrid cap would give maximum rating benefit without exceeding S&P’s threshold — and given ENEL’s current low hybrid ratio, they could issue more.

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<answer>100%</answer>