v3.19.3.a.u2

PPAs and other definite-lived intangible assets and liabilities | 12 Months Ended
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Dec. 31, 2019
PPAs and other definite-lived intangible assets and liabilities |
PPAs and other definite-lived intangible assets and liabilities | 10. PPAs and other definite-lived intangible assets and liabilities Other intangible assets and liabilities include PPAs, fuel supply agreements and capitalized development costs. The following tables summarize the components of our intangible assets and other liabilities subject to amortization at December 31, 2019 and 2018: Assets
|  | Other Intangible Assets, Net
|  | Power Purchase |  |  |
|  | Agreements |  | Total
Gross balances, December 31, 2019 |  | $ | 365.6 |  | $ | 365.6
Less: accumulated amortization |  |  | (221.3) |  |  | (221.3)
Net carrying amounts, December 31, 2019 |  | $ | 144.3 |  | $ | 144.3
|  | Other Intangible Assets, Net
|  | Power Purchase |  |  |
|  | Agreements |  | Total
Gross balances, December 31, 2018 |  | $ | 362.7 |  | $ | 362.7
Less: accumulated amortization |  |  | (192.6) |  |  | (192.6)
Net carrying amounts, December 31, 2018 |  | $ | 170.1 |  | $ | 170.1
Liabilities
|  | Power Purchase and Fuel Supply Agreement Liabilities, Net |
|  | Power Purchase |  | Fuel Supply |  |  |  |
|  | Agreements |  | Agreements |  | Total |
Gross balances, December 31, 2019 |  | $ | (28.1) |  |  | (12.6) |  | $ | (40.7) |
Less: accumulated amortization |  |  | 14.4 |  |  | 6.5 |  |  | 20.9 |
Net carrying amounts, December 31, 2019 |  | $ | (13.7) |  | $ | (6.1) |  | $ | (19.8) |
|  | Power Purchase and Fuel Supply Agreement Liabilities, Net |
|  | Power Purchase |  | Fuel Supply |  |  |  |
|  | Agreements |  | Agreements |  | Total |
Gross balances, December 31, 2018 |  | $ | (28.7) |  |  | (12.6) |  | $ | (41.3) |
Less: accumulated amortization |  |  | 14.0 |  |  | 6.1 |  |  | 20.1 |
Net carrying amounts, December 31, 2018 |  | $ | (14.7) |  | $ | (6.5) |  | $ | (21.2) |
The following table presents amortization expense of intangible assets for the years ended December 31, 2019, 2018 and 2017:
|  | 2019 |  | 2018 |  | 2017 |
PPAs |  | $ | 26.4 |  | $ | 43.4 |  | $ | 36.5 |
Fuel supply agreements |  |  | (0.4) |  |  | (0.4) |  |  | (0.4) |
Total amortization |  | $ | 26.0 |  | $ | 43.0 |  | $ | 36.1 |
The following table presents estimated future amortization expense for the next five years:
Year Ended December 31, |  |  |
2020 |  | $ | 22.1 |
2021 |  |  | 20.2 |
2022 |  |  | 15.9 |
2023 |  |  | 12.6 |
2024 |  |  | 12.6 |
The weighted average remaining amortization period related to our intangible assets and liabilities was 8.6 years as of December 31, 2019.

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