Our operating results are reported in United States dollars. Currently, a 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 may fluctuate in the future, including, as a result of the closing of our sale of the U.K. Portfolio on May 11, 2017. In addition, our investments (including intercompany loans) on 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.
We measure the electricity-generating production capacity of our renewable energy facilities in nameplate capacity. Rated capacity is the expected maximum output a power generation system can produce without exceeding its design limits. 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 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 nameplate capacity of our portfolio is indicative of our overall production capacity and period to period comparisons of our nameplate capacity are indicative of the growth rate of our business. Our renewable energy facilities had an aggregate nameplate capacity of 2,983.1 MW as of December 31, 2016.
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, 2016, 2015 and 2014 were 2,224.7 GWh, 1,972.8 GWh, and 722.4 GWh, respectively. Our GWh sold for wind power plants for the years ended December 31, 2016 and 2015 were 5,499.0 GWh and 1,488.8 GWh, respectively.