Let's work through this step-by-step.

**1. Understanding S&P’s cap for hybrid equity credit**  
S&P caps the equity credit from hybrid bonds at 15% of total adjusted capital (TAC), where TAC = total debt + equity.  
That means hybrids beyond this cap would be treated as 100% debt by S&P, diminishing their credit-enhancing benefit.

**2. Estimating total adjusted capital**  
We use the balance sheet at end-2022 date (2023-01-01 in the facts).  
- **Equity (total)**: €4,894,276,000  
- **Total liabilities**: Total assets (€14,781,520,000) – Equity (€4,894,276,000) = €9,887,244,000  

So TAC (debt + equity) ≈ €14.78 billion.

**3. 15% cap amount**  
15% × €14,781,520,000 ≈ €2,217,228,000.  
This means hybrid bonds up to ~€2.22 billion could get equity credit. Beyond that, no credit.

**4. Current hybrid usage and capacity**  
The company’s “Fondos Propios” (equity) is €4,826,318,000, which includes “Issued Capital” (€270.54m), reserves, etc.  
There’s no explicit line for “hybrid bonds” in the equity section here, suggesting they may not have any now. If they do, it is small relative to the cap.

But the item “Otras Operaciones Con Socios O Propietarios” in equity shows a €920.76m inflow and “Otras Variaciones” shows large reserve movements — likely from a capital increase or hybrid issuance.

**5. Market data context**  
The swap rates and bonds spreads in 2022 are much higher than 2020–2021, raising the cost of issuing hybrids.  
For a company in a regulated, stable sector (electricity transmission), hybrids might be attractive to optimize capital structure, but a full 100% utilization might not be optimal given higher rates and limited need.

**6. How much to use?**  
Given the company already raised substantial funds (likely hybrid or equity-linked) in 2022, the 15% cap gives ample room.  
A rating-conscious firm would probably not push right to the cap given marginal benefit beyond a certain point, but they could easily be at 50–75% of the cap depending on existing issuance.

However, based on the equity movements seen and typical behavior for similar European utilities, 75% utilization is aggressive but plausible, while 100% would risk rating pressure.

**Conclusion**: I estimate the appropriate utilization is 75% of the S&P cap.

<answer>75%</answer>