classified as Level 2 and a discounted cash flow approach using market rates for similar debt instruments. The fair value of the senior notes is based on market price information which is classified as a Level 1 input. They are measured using the last available trades at the end of each respective fiscal year. The fair value of the Senior Notes due 2023, Senior Notes due 2025 and Senior Notes due 2028 were 93.47%, 89.78% and 102.50% of face value as of December 31, 2018, respectively. The fair value of the Senior Notes due 2023, Senior Notes due 2025 and Senior Notes due 2028 were 99.50%, 109.50% and 99.38% of face value as of December 31, 2017, respectively.
Nonrecurring Fair Value Measurements
Assets and liabilities that are measured at fair value on a nonrecurring basis relate primarily to renewable energy facilities, goodwill and intangibles, which are remeasured when the derived fair value is below carrying value on the Company's consolidated balance sheet. For these assets, the Company does not periodically adjust carrying value to fair value except in the event of impairment. When the impairment has occurred, the Company measures the required charges and adjusts the carrying value as discussed in Note 2. Summary of Significant Accounting Policies. For discussion about the impairment testing of assets and liabilities not measured at fair value on a recurring basis see Note 5. Renewable Energy Facilities and Note 7. Goodwill.
14. STOCKHOLDERS' EQUITY
Reduction in SunEdison’s Ownership of Class B Shares
On January 22, 2016, TerraForm Power issued 12,161,844 shares of Class A common stock to affiliates of the D.E. Shaw group, Madison Dearborn Capital Partners IV, L.P. and Northwestern University, and Terra LLC issued 12,161,844 Class A units of Terra LLC to TerraForm Power upon conversion of 12,161,844 Class B shares of TerraForm Power common stock and 12,161,844 Class B units of Terra LLC held by SunEdison. After giving effect to the conversion, SunEdison indirectly owned 48,202,310 Class B shares of TerraForm Power and 48,202,310 Class B units of Terra LLC.
Stockholder Protection Rights Agreement
On July 24, 2016, the Company's Board of Directors (the “Board”) adopted a Stockholder Protection Rights Agreement (the “Rights Agreement”) and declared a dividend of one right on each outstanding share of TerraForm Power Class A common stock. The record date to determine which stockholders were entitled to receive the rights was August 4, 2016. The Rights Agreement was adopted in response to the potential sale of a significant equity stake in the Company by SunEdison and the potential accumulation of TerraForm Power Class A shares. The Rights Agreement and the rights expired in accordance with their terms on August 10, 2017, which was the date of the annual stockholders meeting for 2017 of TerraForm Power.
Merger Consummation and SunEdison Settlement Agreement
As discussed in Note 1. Nature of Operations and Organization, on October 16, 2017, pursuant to the Merger Agreement, Merger Sub merged with and into TerraForm Power, with TerraForm Power continuing as the surviving corporation in the Merger. Immediately following the consummation of the Merger, there were 148,086,027 Class A shares of TerraForm Power outstanding, which excludes 138,402 Class A shares that were issued and held in treasury to pay applicable employee tax withholdings for RSUs held by employees that vested upon the consummation of the Merger. As a result of the Merger, Orion Holdings acquired 51% of TerraForm Power's outstanding Class A shares.
Prior to the consummation of the Merger, SunEdison was the indirect holder of 100% of the shares of Class B common stock of TerraForm Power and held approximately 83.9% of the combined total voting power of the holders of TerraForm Power’s Class A common stock and Class B common stock. As contemplated by the Merger Agreement and in satisfaction of its obligations under the Settlement Agreement, SunEdison exchanged, effective immediately prior to the effective time of the Merger, all of the Class B units of Terra LLC held by it or any of its controlled affiliates for 48,202,310 Class A shares of TerraForm Power. Following completion of this exchange, all of the issued and outstanding shares of Class B common stock of TerraForm Power were automatically redeemed and retired. Pursuant to the Settlement Agreement, immediately following this exchange, the Company issued to SunEdison additional Class A shares such that immediately prior to the effective time of the Merger, SunEdison and certain of its affiliates held an aggregate number of Class A shares equal to 36.9% of TerraForm Power’s fully diluted share count (which was subject to proration based on the Merger consideration election results as