The company’s total adjusted capital (financial debt plus equity) is roughly €11.36 billion. Under S&P Global Ratings’ rule, the maximum equity credit that can be attributed to hybrid instruments is 15 % of this amount, i.e. about €1.70 billion. With net debt of around €4.3 billion and a net‑debt‑to‑EBITDA ratio of about 2.9×, the firm has a solid but moderately leveraged profile. It also faces sizable capex requirements (≈€1.2 billion in 2022) and can benefit from the lower cost of sub‑ordinated financing that hybrid bonds provide while still staying within the rating agency’s ceiling. Issuing hybrid debt up to roughly half of the allowable equity‑credit cap (≈€0.85 billion) would give the company a cost‑effective funding source, improve capital structure, and retain sufficient financial flexibility, making a 50 % utilization the most prudent choice.

<answer>50%</answer>