Energy Efficient Qualified Improvement Property Act of 2021 or the E-QUIP Act This bill allow straight line depreciation over a 10-year period of energy efficient qualified improvement property. The bill defines energy efficient qualified improvement property as any improvement to a building that is nonresidential real property, or multifamily residential rental property, first placed in service more than 10 year before the enactment of this bill, and that is installed as part of the lighting system, the heating, cooling, ventilation, or hot water systems, or the building envelope. The improvement must meet specified performance and other requirements.