Let’s go through the key elements step by step.

**1. Nature of the entity and industry**  
Redeia Corporación SA (formerly Red Eléctrica Corporación) is the Spanish electricity transmission system operator. This is a regulated utility with a natural monopoly, operating under a well-defined regulatory framework in Spain.

**2. Current hybrid situation**  
The facts state:  
- It *issued hybrid bonds in 2021 or 2022*: yes  
- *First year of hybrid bond issuance*: 2023  
This seems partially contradictory – it may indicate they were planning issuance for 2023, but had some hybrid-like instruments already in place.  

More importantly, the guidance emphasizes: *“an entity's previous levels of hybrid bond issuance is a strong indicator of a reasonably advisable level for the next 18 months. In particular, if the entity has not issued hybrid bonds recently, it is a reliable signal that it has reasons not to do so either in the future.”*  
Given that first issuance is in 2023 exactly, and prior issuance was zero or very limited until then, the previous level was effectively 0% for the period under examination (2022 year-end). This points toward a lower allocation now unless circumstances have changed dramatically.

**3. Financial profile**  
- S&P Net Debt / EBITDA 2022: 3.21x  
- S&P FFO / Net Debt 2022: 20.63%  
- Moody’s adjusted leverage trend: Improving  
These metrics are consistent with a solid investment-grade profile (likely ‘BBB+’ to ‘A-’ range). The leverage is moderate and improving. There is no indication of severe rating pressure.

**4. Funding and capex needs**  
From the cash flow statement:  
- Operating cash flow is strong and covers investing outflows, though investing is high (€1.64bn), mainly due to financial instruments and PPE.  
- Financing cash flow shows significant equity inflows (~€989m) and debt repayment. No severe refinancing cliff is evident.  
- Capex on PPE and intangibles is around €536m, manageable within operating cash generation.

**5. Cost of hybrid debt**  
Market data shows:  
- 5Y swap rate moved from negative in 2020–2021 to +1.73% in 2022  
- Sub-senior delta for IG corporates was around 200bps over senior  
The all-in cost for hybrids in 2023 would be materially higher than senior debt. If the issuer has no urgent rating need and debt costs are rising, hybrid issuance becomes less attractive.

**6. Alignment with guidance table**  
The 0% rationale fits well:  
- No current hybrid in capital structure as of 2022 year-end  
- Improving leverage trend  
- Solid rating profile, no extraordinary capex or M&A  
- Materially higher cost of hybrid vs. existing debt  
- No refinancing stress visible  

Given all this, issuance is not required to preserve rating or leverage metrics, and cost would be punitive relative to benefit. Hence, the advisable level is **0%**.

<answer>0%</answer>