The company’s balance‑sheet shows a relatively high leverage (total debt of about €2.3 bn versus equity of €1.5 bn, giving a D/E ratio around 1.5 and a debt‑to‑assets ratio of roughly 36 %). Interest coverage from operating profit is a comfortable 3.5× and operating cash‑flow (€613 m) comfortably exceeds interest expense (€67 m) and provides good headroom for additional financing costs. The regulated energy‑network business generates stable, recurring revenues, which supports a modest level of sub‑ordinated financing.

However, the 2022 market environment saw a sharp rise in risk‑free rates (5‑year swap average moved from –0.26 % in 2021 to +1.73 % in 2022) and credit spreads widened (iBoxx non‑financial IG sub‑senior spread around 2.3 %). This makes senior debt more expensive, and hybrid bonds, which carry a coupon typically above senior spreads, would be even costlier. Nevertheless, hybrid instruments are counted as 50 % equity by rating agencies, providing a way to improve the equity ratio without issuing more costly pure equity.

Given the company’s objective to bring its equity ratio closer to the typical regulated‑utility target (30‑35 %) and to reduce reliance on pure senior debt, a modest proportion of hybrid financing is advisable. An allocation of roughly one‑quarter of total debt (≈ €0.6 bn) would materially lower the D/E ratio, keep interest coverage above the safety threshold, and be consistent with market pricing constraints. A larger share (50 % or more) would push up the overall cost of capital and increase refinancing risk in a rising‑rate environment.

Therefore, a 25 % hybrid‑bond component is the optimal balance between cost, leverage improvement, and financial flexibility.

<answer>25%</answer>