To determine the extent to which REDEIA CORPORACION SA's capital structure should rely on hybrid bonds, we must analyze the fundamental cost and characteristics of the available financing instruments. 

In a standard corporate finance framework, a firm's capital structure aims to minimize its Weighted Average Cost of Capital (WACC) while maintaining a sustainable credit profile. The typical components available are senior debt, equity, and hybrid bonds. 

1. **Cost of Capital Hierarchy**: Senior debt is intrinsically the cheapest form of financing due to its seniority in the capital structure and the tax-deductibility of its interest payments. Equity is the most expensive as it carries the highest risk for investors, but it provides ultimate financial flexibility since dividends are not obligatory.
2. **Role of Hybrid Bonds**: Hybrid bonds blend characteristics of both debt and equity. They are subordinated to senior debt (making them more expensive than senior debt, as indicated by the positive sub-senior delta) but generally rank senior to common equity. While rating agencies may grant hybrid bonds partial equity credit (often up to a certain limit, generally around 15%), they still carry higher yields than standard debt. 
3. **Optimal Reliance**: For a utility like REDEIA CORPORACION SA (formerly Red Eléctrica), its stable, regulated cash flows allow it to sustain a substantial amount of senior debt without incurring excessive financial distress costs. Unless the firm is facing strict rating agency pressure where issuing new equity is too dilutive and senior debt would trigger a downgrade, the optimal, unconstrained capital structure does not strictly *rely* on hybrid bonds. Because senior debt strictly dominates hybrid debt on a cost basis, and equity dominates it on a structural flexibility basis (without default risk), hybrid reliance for standard capital structure optimization defaults to 0% in the absence of explicit structural constraints dictating a subordinated debt buffer.

Therefore, the company should not base its target long-term capital structure strictly on hybrids, relying instead on an optimal mix of senior unsecured debt and equity.

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