This sub-project will evaluate the demand response capability of residential variable capacity heat pump (VCHP) systems. These are "traditional American-style" high static ducked systems. Testing will focus on one to two systems from three to five manufacturers. Lab testing and field testing will be leveraged to evaluate the ability and response of the VCHP system to respond to demand control signals. An appropriate signaling/controlling method will be selected (such as Open ADR 2.0) to enable DR testing at varying operating conditions