CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Project revenue:
Project revenue	$ 62.3	$ 71.3	$ 135.0	$ 144.3
Project expenses:
Fuel	14.1	15.8	33.8	35.8
Operations and maintenance	22.2	18.6	42.7	35.1
Depreciation and amortization	15.2	16.1	30.8	32.3
Total project expenses	51.5	50.5	107.3	103.2
Project other income (loss):
Change in fair value of derivative instruments (Notes 6 and 7)	3.1	(7.0)	(2.5)	(9.4)
Equity in earnings of unconsolidated affiliates (Note 4)	6.1	9.4	19.8	22.3
Interest, net	(0.3)	(0.2)	(0.6)	(0.6)
Other income (expense), net		(1.3)	0.0	(1.2)
Total project other income (loss)	8.9	0.9	16.7	11.1
Project income	19.7	21.7	44.4	52.2
Administrative and other expenses:
Administration	4.5	5.0	11.2	11.8
Interest expense, net	10.2	11.0	21.0	22.1
Foreign exchange loss (gain)	9.3	4.9	(11.3)	9.9
Other (income) expense, net (Note 6)	(1.5)	(3.7)	1.1	0.9
Total administrative and other expenses	22.5	17.2	22.0	44.7
(Loss) income from operations before income taxes	(2.8)	4.5	22.4	7.5
Income tax expense (Note 8)	1.2	1.6	2.7	2.2
Net (loss) income	(4.0)	2.9	19.7	5.3
Net income (loss) attributable to preferred shares of a subsidiary company (Note 11)	1.7	1.7	(4.1)	(4.8)
Net (loss) income attributable to Atlantic Power Corporation	$ (5.7)	$ 1.2	$ 23.8	$ 10.1
Net (loss) earnings per share attributable to Atlantic Power Corporation shareholders: (Note 10)
Basic (in dollars per share)	$ (0.06)	$ 0.01	$ 0.23	$ 0.09
Diluted (in dollars per share)	$ (0.06)	$ 0.01	$ 0.20	$ 0.09
Weighted average number of common shares outstanding: (Note 10)
Basic (in shares)	97.6	109.7	102.4	109.3
Diluted (in shares)	97.6	110.2	130.3	138.0
Energy sales
Project revenue:
Project revenue	$ 31.1	$ 36.5	$ 71.7	$ 73.5
Energy capacity revenue
Project revenue:
Project revenue	27.1	31.6	55.1	61.8
Miscellaneous revenue
Project revenue:
Project revenue	$ 4.1	$ 3.2	$ 8.2	$ 9.0