| Power purchase agreements and other intangible assets and liabilities |
9. Power purchase agreements and other intangible assets and liabilities
Other intangible assets and liabilities include power purchase agreements, fuel supply agreements and capitalized development costs.
The following tables summarize the components of our intangible assets and other liabilities subject to amortization for the years ended December 31, 2015 and 2014:
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Other Intangible Assets, Net
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Power Purchase
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Development
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Agreements
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Costs
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Total
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Gross balances, December 31, 2015
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$
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534.0
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$
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12.9
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$
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546.9
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Less: accumulated amortization
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(225.4)
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(12.6)
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(238.0)
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Net carrying amount, December 31, 2015
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$
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308.6
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$
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0.3
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$
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308.9
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Other Intangible Assets, Net
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Power Purchase
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Development
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Agreements
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Costs
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Total
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Gross balances, December 31, 2014
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$
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563.6
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$
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13.4
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$
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577.0
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Less: accumulated amortization
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(187.4)
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(12.5)
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(199.9)
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Net carrying amount, December 31, 2014
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$
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376.2
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$
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0.9
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$
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377.1
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Power Purchase and Fuel Supply Agreement Liabilities,Net
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Power Purchase
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Fuel Supply
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Agreements
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Agreements
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Total
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Gross balances, December 31, 2015
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$
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(28.4)
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$
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(12.6)
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$
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(41.0)
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Less: accumulated amortization
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9.1
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4.9
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14.0
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Net carrying amount, December 31, 2015
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$
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(19.3)
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$
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(7.7)
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$
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(27.0)
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Power Purchase and Fuel Supply Agreement Liabilities,Net
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Power Purchase
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Fuel Supply
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Agreements
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Agreements
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Total
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Gross balances, December 31, 2014
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$
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(32.2)
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$
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(12.6)
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$
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(44.8)
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Less: accumulated amortization
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7.7
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3.7
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11.4
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Net carrying amount, December 31, 2014
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$
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(24.5)
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$
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(8.9)
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$
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(33.4)
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The following table presents amortization expense of intangible assets for the years ended December 31, 2015, 2014 and 2013:
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2015
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2014
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2013
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Power purchase agreements
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$
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51.3
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$
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57.6
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$
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60.6
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Fuel supply agreements
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(1.2)
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(1.2)
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(1.2)
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Total amortization
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$
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50.1
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$
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56.4
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$
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59.4
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The following table presents estimated future amortization expense for the next five years related to power purchase agreements and fuel supply agreements:
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Power Purchase
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Fuel Supply
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Year Ended December 31,
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Agreements
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Agreements
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2016
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$
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34.9
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$
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(1.2)
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2017
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32.9
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(1.2)
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2018
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26.1
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(1.2)
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2019
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25.4
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(1.2)
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2020
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22.4
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(1.2)
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The following table presents the weighted average remaining amortization period related to our intangible assets as of December 31, 2015:
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Power Purchase
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Fuel Supply
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As of December 31, 2015
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Agreements
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Agreements
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(in years)
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Weighted average remaining amortization period
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7.7
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7.6
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