To determine the extent to which Enel SpA should utilize hybrid bonds relative to S&P Global Ratings' cap, we must calculate the current ratio of hybrid bonds (equity credit) to total adjusted capital and compare it to the 15% limit.

**1. Identify Hybrid Bonds and Equity Credit:**
From the balance sheet data provided for the end of 2022 (2023-01-01 column represents the closing balance for the 2022 fiscal year):
*   **Hybrid Bonds:** The line item "Equity Instruments Perpetual Hybrid Bonds Member" under Equity shows a value of **5,567,000,000 EUR** at 2023-01-01.
*   S&P Global Ratings typically grants 100% equity credit to perpetual hybrid bonds that meet specific criteria (subordination, deferral of coupons, etc.). We assume these instruments qualify for full equity credit as they are classified within equity. Thus, the **Equity Credit from Hybrids = 5,567,000,000 EUR**.

**2. Calculate Total Adjusted Capital:**
S&P defines Adjusted Capital as Debt + Equity.
*   **Total Equity:** The line item "Equity" at 2023-01-01 is **42,082,000,000 EUR**.
*   **Total Debt:** We need to sum interest-bearing debt. Based on the balance sheet:
    *   Long-term Borrowings: 68,191,000,000 EUR
    *   Short-term Borrowings: 18,392,000,000 EUR
    *   Current Portion of Long-term Borrowings: 2,835,000,000 EUR
    *   *Note: Derivatives and other liabilities are generally not included in the core debt definition for this capitalization ratio unless specified as debt-like. We will use standard borrowings.*
    *   Total Debt = 68,191 + 18,392 + 2,835 = **89,418,000,000 EUR**.

*   **Total Adjusted Capital** = Total Debt + Total Equity
    *   Total Adjusted Capital = 89,418,000,000 + 42,082,000,000 = **131,500,000,000 EUR**.

**3. Calculate the Current Hybrid Ratio:**
*   Ratio = (Equity Credit from Hybrids / Total Adjusted Capital)
*   Ratio = 5,567,000,000 / 131,500,000,000
*   Ratio ≈ **4.23%**

**4. Compare to S&P Cap:**
*   S&P Cap = 15% of Total Adjusted Capital.
*   Maximum Allowable Hybrid Equity Credit = 0.15 * 131,500,000,000 = 19,725,000,000 EUR.
*   Current Hybrid Amount = 5,567,000,000 EUR.

**5. Determine Utilization Extent:**
The question asks "To what extent should this company utilize hybrid bonds relative to S&P Global Ratings' cap". This implies calculating the percentage of the available cap that is currently being used or should be used to optimize the capital structure without breaching the rating agency's limit for equity credit.

However, the options (0%, 25%, 50%, 75%, 100%) usually refer to the *proportion of the cap utilized*.
*   Current Utilization of Cap = (Current Hybrids / Max Allowable Hybrids)
*   Current Utilization = 5,567 / 19,725 ≈ **28.2%**

Looking at the options: 0%, 25%, 50%, 75%, 100%.
The current utilization is approximately 28%, which is closest to **25%**.

Alternatively, if the question implies "what percentage of the *cap* represents the optimal usage", companies often aim to maximize equity credit to strengthen their balance sheet ratings up to the cap. However, "should utilize... relative to the cap" combined with the current state suggests assessing the current position. The company is currently using about 28% of its allowed capacity. It has significant room to issue more hybrids (up to ~14 billion EUR more) before hitting the 15% total capital cap.

Let's re-read carefully: "To what extent should this company utilize hybrid bonds relative to S&P Global Ratings' cap... Options are 0%, 25%, 50%, 75%, or 100%?"

If the question is asking for the *current* utilization level relative to the cap, the answer is ~28%, which rounds to 25%.
If the question is asking for a *recommendation* on how much of the cap to fill, companies typically do not fill 100% of the cap due to cost and complexity, but 25-50% is common. Given the current level is ~28%, and the company has been active in this market (issuing 3.18B in 2021, 0 in 2022), maintaining a level around 25-30% of the cap is a reasonable interpretation of the current status.

Let's check if there is a different interpretation. Is the "Equity" figure already adjusted? S&P adjustments might add back certain items. However, using the reported numbers:
Hybrids: 5.57B
Total Capital (Debt+Equity): 131.5B
Hybrid % of Capital: 4.2%
Cap: 15%
Utilization of Cap: 4.2% / 15% = 28%.

The closest option to 28% is 25%.

<answer>25%</answer>