VEIC conducted a study to examine the market opportunity and technology performance of 120-volt and 240-volt (120V/240V) variable speed, high-efficiency in-unit heat pumps for use in direct replacement of less efficient room air conditioning units and displacing or replacing in-unit gas or electric heating in California multifamily buildings. The market opportunity and technology performance are examined and informed through a review of the existing multifamily building stock in California and a technical review of new in-unit heat pump solutions, building energy modeling, and interviews with key market stakeholders including manufacturers, multifamily program implementers, consultants and property managers, and national, regional, and state level energy efficiency organizations.