Basic earnings (loss) per share is calculated by dividing net income (loss) by the weighted average common shares outstanding during their respective period. Diluted earnings (loss) per share is computed including dilutive potential shares as if they were outstanding shares during the year. Dilutive potential shares include shares that would be issued if all of the convertible debentures were converted into shares at January 1, 2012. Dilutive potential shares also include the weighted average number of shares, as of the date such notional units were granted, that would be issued if the unvested notional units outstanding under the LTIP were vested and redeemed for shares under the terms of the LTIP.

The following table sets forth the diluted net income and potentially dilutive shares utilized in the per share calculation for the three months ended March 31, 2012 and 2011:

	2012			2011

Numerator:
Net income (loss) attributable to Atlantic Power Corporation	$	(42,292	)	$	6,136
Denominator:
Weighted average basic shares outstanding		113,578			67,654
Dilutive potential shares:
Convertible debentures		13,252			14,809
LTIP notional units		478			517

Potentially dilutive shares		127,308			82,980

Diluted EPS	$	(0.37	)	$	0.09

Potentially dilutive shares from convertible debentures and potentially dilutive shares from LTIP notional units have been excluded from fully diluted shares in the three months ended March 31, 2012 because their impact would be anti-dilutive. Potentially dilutive shares from convertible debentures have been excluded from fully diluted shares in the three-month period ended March 31, 2011 because their impact would be anti-dilutive.