To determine the appropriate level of hybrid bond issuance for Red Eléctrica Corporación, S.A. (REDEIA), we need to analyze its financial profile, credit metrics, and funding needs based on the provided 2022 annual report data, and then map these to the hybrid issuance guidelines.

**1. Current Financial Position and Credit Metrics:**
REDEIA is a regulated utility (electricity transmission) with a stable business model, but it currently carries relatively high leverage. 
- **Total Financial Debt:** Sum of long-term borrowings (€5,491.1M) and current borrowings (€721.8M) plus other noncurrent/current financial liabilities (€52.6M + €983.4M) totals approximately €6,248.9M. Even just taking standard borrowings gives €6,212.9M.
- **Equity:** Total equity stands at €4,894.3M (or €4,826.3M in "Fondos Propios").
- **Adjusted Leverage (Debt / (Debt + Equity)):** Using total borrowings of ~€6.2B and equity of ~€4.9B, the debt-to-capital ratio is roughly 56%. For regulated utilities, leverage in the mid-to-high 50s often leaves limited headroom at the 'BBB+'/'A-' rating thresholds, meaning there is moderate pressure to optimize the capital structure.
- **Cash Flow and Capex:** Operating cash flow was €1.57B, while investing activities consumed €1.64B (driven by heavy investment purchases of €2.37B, offset by financial asset movements). This indicates a high capex intensity, requiring robust funding.

**2. Refinancing and Funding Needs:**
REDEIA has significant refinancing needs. Current borrowings and the current portion of noncurrent borrowings stand at €1.39B (as of Jan 1, 2022) and €721.8M (as of Jan 1, 2023). Additionally, long-term borrowings decreased from €5.89B to €5.49B, showing active debt management. The combination of high capex and looming maturities creates a moderate-to-high need for funding.

**3. Hybrid Bonds Rationale:**
Given the leverage pressure (Debt/Capital ~56%) and the high capex intensity, REDEIA has a strong rationale to issue hybrid bonds to optimize its capital structure. Hybrids receive partial (50%) or full equity credit from S&P depending on their features, which meaningfully improves adjusted leverage metrics (reducing Debt/Capital) and provides valuable rating headroom for a utility carrying substantial debt.

**4. Cost of Debt and Market Conditions:**
- The 5Y Swap Curve rose significantly in 2022 to 1.726%, and the 10Y to 1.927%.
- Corporate spreads (iShares Core Euro Corp Bond) are around 1.085%, and sub-senior spreads are higher at 2.295%.
- Since REDEIA has existing senior unsecured debt, issuing hybrid bonds (which are subordinated) will increase the blended cost of debt, but the incremental cost is justifiable to secure the equity credit and protect the investment-grade profile. 

**5. Sizing the Hybrid Issuance:**
S&P limits equity credit from hybrids to a maximum of 15% of total adjusted capital. 
- 15% is generally reserved for transformational M&A or severe downgrade risk (not the case here, as the business remains stable and regulated).
- 11.25% applies to high capex intensity OR large acquisition pipeline with significant leverage pressure. REDEIA has high capex and moderate leverage pressure, but its regulated cash flows are highly predictable, making 11.25% slightly aggressive.
- **7.5%** fits best: REDEIA has moderate refinancing/acquisition needs, leverage that is moderately constrained (needing optimization), and hybrid issuance would meaningfully improve adjusted leverage metrics while the cost of hybrid will slightly increase the current cost of debt. A 7.5% hybrid issuance relative to total capital (~€462M) is well within the annual €3B limit and represents a prudent, standard utility hybrid stack.

<answer>7.5%</answer>