Let’s go through the reasoning step by step.

**1. Capital structure overview**  
From the balance sheet data at the end of 2022 (2023-01-01):  
- Total Equity = €1,517,534,000  
- Total Liabilities = €4,934,062,000  
- Total Debt (Long-term + Current borrowings) = €1,695,362,000 + €638,944,000 = €2,334,306,000  
- Total Adjusted Capital (Debt + Equity) = €2,334,306,000 + €1,517,534,000 = €3,851,840,000  

S&P’s 15% cap on hybrids = 15% × €3,851.84M ≈ €577.8M.

**2. Current use of hybrids**  
The balance sheet doesn’t explicitly show hybrid bonds under equity or liabilities. The “Equity” section doesn’t list any hybrid instruments, and borrowings seem to be conventional. That suggests the company is at 0% of the 15% cap currently.

**3. Rationale for issuing hybrids**  
The company’s debt-to-equity ratio is about 1.54×, which is moderately leveraged for a regulated network utility.  
- Interest rates in 2022 are significantly higher (e.g., 10Y swap ~1.93%) compared to prior years, making hybrid issuance more expensive.  
- The company has stable operating cash flows (~€613M from operations), enough to cover interest and dividends.  
- Profitability is solid, and financing needs seem manageable given the investment program (~€200M intangible/PPE capex annually).  
- Given higher financing costs and no apparent urgent need to improve credit metrics, issuing up to the full 15% limit seems unnecessary and costly.

**4. Appropriate utilization**  
A conservative utility like REN would likely use hybrids sparingly, mostly to maintain headroom within rating thresholds during large capex cycles. The data doesn’t show distress, so a modest percentage of the cap seems reasonable, but 0% is also plausible if management is conservative.  

Taking into account the rising rate environment and moderate leverage, something like 25% of the cap (i.e., ~€144M) could be a balanced approach — enough to optimize capital structure but not over-rely on expensive subordinated debt. However, given there is no indication they *need* to issue, the most prudent answer based only on these facts would be **0%**.

<answer>0%</answer>