Hybrid bonds should be utilized up to the cap set by S&P Global Ratings, which allows equity credit for hybrids up to 15% of total adjusted capital (debt + equity). The data provided show Acciona has a sizable equity base and significant liabilities, with equity around 6,304,000,000 EUR and noncurrent liabilities around 8,467,000,000 EUR, plus other current and noncurrent liabilities. Total adjusted capital = debt + equity. Using hybrids would count towards equity credit up to 15% of that total. Since the question asks to choose among discrete options (0%, 25%, 50%, 75%, 100%), and the cap is 15%, the feasible practical utilization aligned with the cap is 0% (i.e., do not exceed 15% equity credit; choosing 0% ensures compliance and avoids overstretching the cap). Therefore, the extent should be 0%. 
<answer>0%</answer>