the capital markets several times in 2017, including in connection with our New Revolver, New Term Loan, the New Senior Notes due 2023 and the Senior Notes due 2028 (as defined and discussed in Financing Activities within Liquidity and Capital Resources below), each of which we incurred in the fourth quarter of 2017. We also plan to access the capital markets in connection with financing our recently announced acquisition of Saeta Yield that is expected to close in the second quarter of 2018. Limitations on our ability to access the corporate and project finance debt and equity capital markets in the future on terms that are accretive to our existing cash flows would be expected to negatively affect our results of operations, business and future growth.
Our operating results are reported in United States dollars. Currently, a substantial majority of our revenues and expenses are generated in U.S. Dollars. Historically, we have also had significant revenue and expenses generated in other currencies, including the British Pound and the Canadian dollar. This mix of currencies changed over the course of 2017 as a result of the closing of the sale of substantially all of our portfolio of solar power plants located in the U.K. (24 operating projects representing an aggregate 365.0 MW, the “U.K. Portfolio”) on May 11, 2017. This mix may continue to change in the future if we elect to alter the mix of our portfolio within our existing markets or elect to expand into new markets, including as a result of the recently announced acquisition of Saeta Yield, a Spanish corporation, that is expected to close in the second quarter of 2018. In addition, our investments (including intercompany loans) in renewable energy facilities in foreign countries are exposed to foreign currency fluctuations. As a result, we expect our revenues and expenses will be exposed to foreign exchange fluctuations in local currencies where our renewable energy facilities are located. To the extent we do not hedge these exposures, fluctuations in foreign exchange rates could negatively impact our profitability and financial position.
Net nameplate capacity
We measure the electricity-generating production capacity of our renewable energy facilities in net nameplate capacity. Rated capacity is the expected maximum output a power generation system can produce without exceeding its design limits. Net nameplate capacity is the rated capacity of all of the renewable energy facilities we own adjusted to reflect our economic ownership of joint ventures and similar power generation facilities. We measure net nameplate capacity for solar generation facilities in MW (DC) and for wind power plants in MW (AC). The size of our renewable energy facilities varies significantly among the assets comprising our portfolio. We believe the combined net nameplate capacity of our portfolio is indicative of our overall production capacity and period to period comparisons of our net nameplate capacity are indicative of the growth rate of our business. Our renewable energy facilities had an aggregate net nameplate capacity of 2,606.4 MW as of December 31, 2017.
Gigawatt hours sold
Gigawatt hours sold refers to the actual volume of electricity sold by our renewable energy facilities during a particular period. We track gigawatt hours sold as an indicator of our ability to realize cash flows from the generation of electricity at our renewable energy facilities. Our GWh sold for solar generation facilities for the years ended December 31, 2017, 2016 and 2015 were 1,895 GWh, 2,225 GWh and 1,973 GWh, respectively. Our GWh sold for wind power plants for the years ended December 31, 2017, 2016 and 2015 were 5,381 GWh, 5,499 GWh and 1,489 GWh, respectively.