To evaluate how much hybrid‑bond capacity ENEL can use we first compute total adjusted capital as defined by S&P (financial debt + equity + hybrid bonds).  

- Financial debt (long‑term borrowings + short‑term borrowings + current portion of long‑term borrowings):  
  68 191 + 18 392 + 2 835 = 89 418 million EUR.  

- Equity (as reported): 42 082 million EUR.  

- Hybrid bonds (perpetual hybrid bonds): 5 567 million EUR.  

Total adjusted capital = 89 418 + 42 082 + 5 567 = 137 067 million EUR.  

S&P’s cap allows equity credit from hybrids up to 15 % of this amount:  
15 % × 137 067 ≈ 20 560 million EUR of equity credit.  

Current equity credit from the existing hybrids = 0.5 × 5 567 ≈ 2 784 million EUR, which is only about 13.5 % of the permitted 20 560 million EUR.  
Thus ENEL has ample room to increase its hybrid‑bond issuance up to the cap if desired.

Given the low coupon cost (≈2.2 % vs market rates) and the substantial unused capacity, the company can safely target the maximum allowed usage.  

**Therefore, the company should utilize hybrid bonds to the full extent permitted by the rating agency’s cap.**  

<answer>100%</answer>