The majority of the Corporation's revenues are derived from the sale of physical power, capacity and environmental attributes, leasing of power facilities, and from asset optimization activities, which the Corporation disaggregates into the following groups for the purpose of determining how economic factors affect the recognition of revenue.


Year ended Dec. 31, 2020	Hydro	Wind and Solar	North American Gas(1)	Australian Gas	Alberta Thermal(2)	Centralia(2)	Energy Marketing	Corporate and Other	Total
Revenues from contracts with customers	141	261	196	90	325	10	—	—	1,023
Revenue from leases(3)	—	—	8	60	55	—	—	—	123
Revenue from derivatives and other trading activities	—	(2)	4	—	(12)	283	122	12	407
Government incentives	1	4	—	—	—	—	—	—	5
Revenue from other(4)	10	66	9	8	251	204	—	(5)	543
Total revenue	152	329	217	158	619	497	122	7	2,101

Revenues from contracts with customers
Timing of revenue recognition
At a point in time	—	25	—	—	23	10	—	—	58
Over time	141	236	196	90	302	—	—	—	965
Total revenue from contracts with customers	141	261	196	90	325	10	—	—	1,023

(1) This segment was previously known as the Canadian Gas segment but renamed with the acquisition of the US cogeneration facility in the second quarter of 2020. Refer to Note 4(K) for further details. In addition, during the third quarter of 2020, merchant revenue within this segment was reclassified from revenue from contracts with customers to revenue from other and prior periods were adjusted.


Year ended Dec. 31, 2019	Hydro	Wind and Solar	North American Gas(1)	Australian Gas	Alberta Thermal(2)	Centralia(2)	Energy Marketing	Corporate and Other	Total
Revenues from contracts with customers	142	244	190	87	395	10	—	—	1,068
Revenue from leases(3)	—	—	—	65	65	—	—	—	130
Revenue from derivatives and other trading activities	—	18	2	—	(17)	160	129	4	296
Government incentives	—	8	—	—	—	—	—	—	8
Revenue from other(4)	14	42	17	8	373	401	—	(10)	845
Total revenue	156	312	209	160	816	571	129	(6)	2,347

Revenues from contracts with customers
Timing of revenue recognition
At a point in time	—	27	—	—	41	10	—	—	78
Over time	142	217	190	87	354	—	—	—	990
Total revenue from contracts with customers	142	244	190	87	395	10	—	—	1,068


Year ended Dec. 31, 2018	Hydro	Wind and Solar	North American Gas(1)	Australian Gas	Alberta Thermal(2)	Centralia(2)	Energy Marketing	Corporate	Total
Revenues from contracts with customers	132	206	206	91	517	9	—	—	1,161
Revenue from leases(3)	7	27	—	68	68	—	—	—	170
Revenue from derivatives and other trading activities	—	(20)	4	—	(1)	115	67	—	165
Government incentives	—	16	—	—	—	—	—	—	16
Revenue from other(4)	17	53	22	6	328	318	—	(7)	737
Total revenue	156	282	232	165	912	442	67	(7)	2,249

Revenues from contracts with customers
Timing of revenue recognition
At a point in time	—	18	—	—	38	9	—	—	65
Over time	132	188	206	91	479	—	—	—	1,096
Total revenue from contracts with customers	132	206	206	91	517	9	—	—	1,161


Contract liabilities	2020	2019
Balance, beginning of the year	15	88
IFRS 16 transition adjustments(1)	—	15
Amounts transferred to revenue included in opening balance	(1)	(10)
Consideration received	1	5
Increases due to interest accrued and expensed during the period	—	5
Contract termination associated with the purchase of Keephills 3 (Note 4(R))	—	(88)
Consideration paid	2	—
Performance obligations satisfied	(2)	—
Balance, end of year	15	15
Current portion	1	1
Long-term portion	14	14

(1) In 2019, on transition to IFRS 16, some contracts that were previously considered leases under IAS 17 did not meet the definition of a lease under IFRS 16 and therefore were assessed under IFRS 15 and balances were transferred from deferred revenue to contract liabilities.

The opening contract liabilities in 2019 were primarily comprised of consideration received from the Corporation’s Keephills 3 joint operation partner, Capital Power, for which the Corporation had a future obligation to transfer goods and services to Capital Power under the contract. On closing of the Keephills 3 and Genesee 3 swap, wherein the Corporation acquired Capital Power's 50 per cent ownership interest in Keephills 3 and sold its 50 per cent ownership interest in Genesee 3, the agreement with Capital Power was terminated in 2019 and the Corporation no longer had any further performance obligations and the related contract liability balance was recognized in net earnings.

The following disclosures regarding the aggregate amounts of transaction prices allocated to remaining performance obligations (contract revenues that have not yet been recognized) for contracts in place at the end of the reporting period exclude revenues related to contracts that qualify for the following practical expedients:

▪The Corporation recognizes revenue from the contract in an amount that is equal to the amount invoiced where the amount invoiced represents the value to the customer of the service performed to date. Certain of the Corporation’s contracts at some of its wind, hydro, gas and solar facilities, and within its commercial and industrial business, qualify for this practical expedient. For these contracts, the Corporation is not required to disclose information about the remaining unsatisfied performance obligations.

Additionally, in many of the Corporation’s contracts, elements of the transaction price are considered constrained, such as for variable revenues dependent upon future production volumes that are driven by customer or market demand or market prices that are subject to factors outside the Corporation’s influence. Future revenues that are related to constrained variable consideration are not included in the disclosure of remaining performance obligations until the constraints are resolved. Further, adjustments to revenue to recognize a significant financing component in a contract are not included in the amounts disclosed for remaining performance obligations.

At Dec. 31, 2020, the Corporation's PPA with the Balancing Pool to provide the capacity of 12 hydro facilities throughout the province of Alberta concluded. Future production will be sold into the merchant market. The Corporation has contracts for blackstart services at specific hydro facilities, which will conclude at the end of 2030. The Corporation also has a contract with the Government of Alberta to manage water on the Bow River for flood and drought mitigation purposes, which concludes in 2021.

Estimated future revenues related to the remaining performance obligations for these contracts as of Dec. 31, 2020, are approximately $31 million, which the Corporation expects to recognize approximately $8 million in 2021 and approximately $2 million to $3 million annually from 2022-2030.

The practical expedient allowing the recognition of revenue from the contract in an amount that is equal to the amount invoiced is applied to all hydro energy contracts in Ontario, British Columbia and Washington; accordingly, disclosures related to remaining performance obligations are not provided for these contracts.

At Dec. 31, 2020, the Corporation had long-term contracts with customers to deliver electricity and the associated renewable energy credits from three wind facilities located in Alberta, Minnesota and Quebec, for which the invoice practical expedient is not applied. The PPAs generally require all available generation to be provided to customers at fixed prices, with certain pricing subject to annual escalations for inflation. The Corporation expects to recognize such amounts as revenue as it delivers electricity over the remaining terms of the contracts, until 2024, 2034 and 2033, respectively. Electricity delivered is ultimately dependent upon the wind resource, which is outside of the Corporation’s control. Amounts delivered, and therefore revenue recognized, in the future will vary. These variable revenues for electricity delivered are considered to be fully constrained, and will be recognized over time as the performance obligation, the delivery of electricity, is satisfied. Accordingly, these revenues are excluded from these disclosures. The Corporation also has contracts to sell renewable energy certificates generated at merchant wind facilities and expects to recognize revenues as it delivers the renewable energy certificates to the purchasers over the remaining terms of the contracts, from 2020 through 2024.

Estimated future revenues related to the remaining performance obligations for these contracts as of Dec. 31, 2020, are approximately $13 million, of which the Corporation expects to recognize between approximately $2 million to $5 million annually through to contract expiry.

The practical expedient allowing the recognition of revenue from the contract in an amount that is equal to the amount invoiced is applied to wind energy contracts in Ontario, New Brunswick, Quebec and Wyoming, and for all solar contracts; accordingly, disclosures related to remaining performance obligations are not provided for these contracts.

At Dec. 31, 2020, the Corporation has contracts with customers to deliver energy services from one of its gas facilities in Ontario. The contracts all consist of a single performance obligation requiring the Corporation to stand ready to deliver electricity and steam. A summary of the key terms of these contracts is set out below.

The energy supply agreements require specified amounts of steam to be delivered to each customer, and have pricing terms that include fixed and variable charges for electricity, capacity and steam, as well as a true-up based on contractual minimum volumes of steam. The steam reconciliation is based on an estimate of the customer’s steam volume taken and the contractual minimum volume, and various factors including the annual average market price of electricity and the average locally posted and index prices of natural gas, as well as transportation. For steam volumes not taken by the customer, a revenue-sharing mechanism provides for sharing of revenues earned by the Corporation using that steam to generate and sell electricity. Capacity and electricity pricing vary from contract to contract and are subject to annual indexation at varying rates. Electricity and steam delivered is ultimately dependent upon customer requirements, which is outside of the Corporation’s control. The variable revenues under the contracts are considered to be fully constrained. Accordingly, these revenues are excluded from these disclosures. The Corporation expects to recognize revenue as it delivers electricity and steam until the completion of the contract in late 2022.

At the same gas facility, the Corporation has a contract with the local power authority with fixed capacity charges that are adjusted for seasonal fluctuations, steam demand from the plant’s other customers and for deemed net revenue related to production of electricity into the market. As a result, revenues recognized in the future will vary as they are dependent upon factors outside of the Corporation’s control and are considered to be fully constrained. Accordingly, these revenues are excluded from these disclosures. The Corporation expects to recognize such revenue as it stands ready to deliver electricity until the completion of the contract term on Dec. 31, 2025.

At Dec. 31, 2020, the Corporation had contracts with customers to deliver steam, hot water and chilled water from one of its other gas facilities in Ontario, extending through 2023. Prices under these contracts are at fixed base amounts per gigajoule and are subject to escalation annually for both gas prices and inflation. The contracts include minimum annual take-or-pay volumes.

The Corporation's contract with its customer for provision of steam and electricity output at its Alberta cogeneration facility, effective Jan. 1, 2020 through Dec. 31, 2029, is considered an operating lease resulting in some revenues being classified for accounting purposes as variable lease revenues. Other revenue streams are based on cost-recovery mechanisms and thus are variable in nature and are considered to be fully constrained and excluded from these disclosures.

Estimated future revenues related to the remaining performance obligations for these contracts as of Dec. 31, 2020, are approximately $13 million in total, of which the Corporation expects to recognize between approximately $4 million to $5 million annually for the duration of the contracts.

The practical expedient allowing the recognition of revenue from the contract in an amount that is equal to the amount invoiced is applied to some of the Corporation’s other gas facilities’ contracts in Ontario and the United States; accordingly, disclosures related to remaining performance obligations are not provided for these contracts.

At Dec. 31, 2020, the Corporation has PPAs with customers to deliver electricity from its gas facilities located in Australia. The PPAs generally call for all available generation to be provided to customers. Pricing terms include fixed and variable price components for delivered electricity and fixed capacity payments. Prices may be subject to true-up adjustments for deviations from expected heat rates and are subject to various escalators to reflect inflation. Electricity delivered is ultimately dependent upon customer requirements, which is outside of the Corporation’s control. These variable revenues for electricity delivered are considered to be fully constrained, and will be recognized at a point in time as the performance obligation, the delivery of electricity, is satisfied. Accordingly, these revenues are excluded from these disclosures. The contracts have durations that range from 2026 to 2042.

One of the Corporation's PPA with its customer to deliver electricity from its gas facilities is considered a finance lease resulting in some revenues being classified for accounting purposes as finance lease income. The Corporation also earns revenues from providing operation and maintenance services for the facility for a fixed monthly fee. Pricing is subject to periodic review under the PPA and subject to escalation to reflect inflation out to the end of the contract in 2038. Other revenue streams are based on cost-recovery mechanisms and thus are variable in nature and considered to be fully constrained and excluded from these disclosures.

Estimated future revenues related to the remaining performance obligations for these contracts as at Dec. 31, 2020, are approximately $2,594 million, of which the Corporation expects to recognize approximately $203 million in total over the next two fiscal years and on average, between approximately $100 million to $126 million annually thereafter for the duration of the remaining contract.

The Corporation also has several contracts for sale of byproducts of coal combustion from certain of its coal facilities. The contracts range in duration from one to three years. Generally, revenues vary based on market prices that are subject to factors outside of the Corporation’s control, and the quantities delivered and sold, which are ultimately dependent upon customer demand. These variable revenues are considered to be fully constrained, and will be recognized at a point in time as the performance obligation, the delivery of byproducts, is satisfied. Accordingly, these revenues are excluded from these disclosures.

The Corporation has a contract, commencing in late 2023, for the sale of capacity and electricity, exercisable at the option of the customer, under which the Corporation will receive a fixed capacity payment and variable energy payments based on production. Estimated future revenues related to the remaining performance obligations for these contracts as of Dec. 31, 2020, are approximately $336 million, of which the Corporation expects to recognize on average, between $5 million to $10 million in 2023 and $40 million to $45 million annually thereafter for the duration of the contracts.

The Corporation’s long-term contract for the sale of electricity produced at its US Coal plant is considered a derivative and is designated as an all-in-one hedge. Accordingly, while revenues for electricity delivered to the customer are recognized pursuant to the contractual terms, the revenues are not accounted for under IFRS 15 and the contract has been excluded from any required IFRS 15 disclosures.

The Corporation also has a contract for the sale of byproducts of coal combustion from its US Coal plant. Generally, revenues vary based on market prices that are subject to factors outside of the Corporation’s control, and the quantities delivered and sold, which are ultimately dependent upon customer demand. These variable revenues are considered to be fully constrained, and will be recognized at a point in time as the performance obligation, the delivery of byproducts, is satisfied. Accordingly, these revenues are excluded from these disclosures.