Foreign Currency Risk
During the year ended December 31, 2018, we generated operating revenues in the United States (including Puerto Rico), Canada, Spain, Portugal, the United Kingdom, Chile and Uruguay, with our revenues being denominated in U.S. dollars, Euro, Canadian dollars and British pounds. The PPAs, operating and maintenance agreements, financing arrangements and other contractual arrangements relating to our current portfolio are denominated in U.S. dollars, Euro, Canadian dollars and British pounds.
We use currency forward contracts in certain instances to mitigate the financial market risks of fluctuations in foreign currency exchange rates. We manage our foreign currency exposures through the use of these currency forward contracts to reduce risks arising from the change in fair value of certain assets, liabilities and intercompany loans denominated in Euro.
We use foreign currency forward contracts to hedge portions of our net investment positions in certain subsidiaries with Euro and Canadian dollar functional currencies and to manage our foreign exchange risk. For instruments that are designated and qualify as hedges of net investments in foreign operations, the effective portion of the net gains or losses attributable to changes in exchange rates are recorded in foreign currency translation adjustments accumulated other comprehensive income (“AOCI”). Recognition in earnings of amounts previously recorded in AOCI is limited to circumstances such as complete or substantial liquidation of the net investment in the hedged foreign operation. The objective of these practices is to minimize the impact of foreign currency fluctuations on our operating results. We estimate that a hypothetical 100 bps, or 1%, increase or decrease in Euros would have increased or decreased our earnings by $7.1 million for the year ended December 31, 2018. Cash flows from derivative instruments designated as net investment hedges and non-designated derivatives used to manage foreign currency risks associated with intercompany loans are classified as investing activities in the consolidated statements of cash flows. Cash flows from all other derivative instruments are classified as operating activities in the consolidated statements of cash flows.
For certain of our wind power plants, we may use long-term cash-settled swap agreements to economically hedge commodity price variability inherent in wind electricity sales arrangements. If we sell electricity generated by our wind power plants to an independent system operator market and there is no PPA available, then we may enter into a commodity swap to hedge all or a portion of the estimated revenue stream. These price swap agreements require periodic settlements, in which we receive a fixed-price based on specified quantities of electricity and we pay the counterparty a variable market price based on the same specified quantity of electricity. We estimate that a hypothetical 10% increase or decrease in electricity sales prices pertaining to commodity swaps not designated as hedges would have decreased or increased our earnings by $12.7 million or $13.5 million for the year ended December 31, 2018, respectively.
Our principal liquidity requirements are to finance current operations, service debt and to fund cash dividends to investors. Changes in operating plans, lower than anticipated electricity sales, increased expenses, acquisitions or other events may cause management to seek additional debt or equity financing in future periods. There can be no guarantee that financing will be available on acceptable terms or at all. Debt financing, if available, could impose additional cash payment obligations and additional covenants and operating restrictions. Our ability to meet our debt service obligations and other capital requirements, including capital expenditures, as well as make acquisitions, will depend on our future operating performance which, in turn, will be subject to general economic, financial, business, competitive, legislative, regulatory and other conditions, many of which are beyond management's control.
Counterparty Credit Risk
Credit risk relates to the risk of loss resulting from non-performance or non-payment by offtake counterparties under the terms of their contractual obligations, thereby impacting the amount and timing of expected cash flows. We monitor and manage credit risk through credit policies that include a credit approval process and the use of credit mitigation measures such as having a diversified portfolio of creditworthy offtake counterparties. As of December 31, 2018, on a weighted average basis (based on MW), our PPA counterparties had an investment grade credit rating. However, there are a limited number of offtake counterparties under offtake agreements in each region that we operate, and this concentration may impact the overall exposure to credit risk, either positively or negatively, in that the offtake counterparties may be similarly affected by changes in economic, industry or other conditions.