Credit Ratings
| Year | Rating Agency | Credit Rating | Rating Outlook | |
| Long-term | Short-term | |||
| 2024 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2023 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2022 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2021 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2020 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2019 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2018 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2017 | FitchRatings | AA+(twn) | F1+(twn) | Stable |
| 2016 | FitchRatings | AA(twn) | F1+(twn) | Stable |
| 2015 | FITCH IBCA | AA(twn) | F1+(twn) | Stable |