To determine the extent to which REN should utilize hybrid bonds relative to the 15% S&P equity credit cap, we evaluate the company's financial position and cost of debt.

1.  **Capital Structure Analysis**: REN’s total equity at the end of 2022 is 1,517,534,000 EUR. Its total debt (Long-term borrowings + Current borrowings) is 1,695,362,000 + 638,944,000 = 2,334,306,000 EUR. Total capital (Debt + Equity) is approximately 3,851,840,000 EUR.
2.  **S&P Hybrid Cap**: The cap on equity credit is 15% of the total adjusted capital (3,851,840,000 * 0.15 = 577,776,000 EUR).
3.  **Cost of Debt Environment**: The provided swap curve data shows a significant increase in interest rates between 2021 and 2022 (e.g., 10Y swap rising from 0.053% to 1.927%). Furthermore, the iBoxx EUR Non-Financial IG spread (adjusted for delta) rose from 1.298% to 2.295%. This indicates that issuing new debt has become substantially more expensive.
4.  **Strategic Use of Hybrids**: Hybrid bonds provide an opportunity for REN to optimize its capital structure by obtaining partial equity credit (up to 15% of total capital) while managing its debt profile. Given the rising interest rate environment and the need for capital intensive investments (evident in the high level of intangible assets and the Transitional Gas Price Stabilization Regime impact), maximizing the allowable equity credit through hybrid financing is financially prudent to support the balance sheet without triggering full equity dilution or credit rating downgrades.

Given the capacity to utilize the 15% limit fully to optimize the weighted average cost of capital (WACC) in an increasing rate environment, utilizing the maximum limit is the standard approach for entities with stable, regulated cash flows like REN.

<answer>100%</answer>