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Income tax Income tax (Tables) | 3 Months Ended
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Mar. 31, 2018
Income Tax Disclosure [Abstract] |
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] | The significant differences between the U.S. Federal statutory rate and PGE’s effective tax rate for financial reporting purposes are as follows:
| Three Months Ended March 31, |
| 2018 |  | 2017 |
Federal statutory tax rate | 21.0 | % |  | 35.0 | % |
Federal tax credits* | (18.0 | ) |  | (16.1 | ) |
State and local taxes, net of federal tax benefit | 6.5 |  |  | 5.0 |  |
Flow through depreciation and cost basis differences | 1.0 |  |  | 1.0 |  |
Other | 0.6 |  |  | (0.9 | ) |
Effective tax rate | 11.1 | % |  | 24.0 | % |
* Federal tax credits consists of production tax credits (PTCs) earned from Company-owned wind-powered generating facilities. The federal PTCs are earned based on a per-kilowatt hour rate, and as a result, the annual amount of PTCs earned will vary based on weather conditions and availability of the facilities. The PTCs are generated for 10 years from the corresponding facilities’ in service dates. PGE’s PTC generation ends at various dates between 2017 and 2024.

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- Definition Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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