High efficiency low voltage DC-DC conversion is a key enabler to the design of power-efficient integrated circuits. Typically a star configuration of the DC-DC converters, where only one converter resides between the source and each load, is used to deliver currents with appropriate voltage levels to different loads in the circuit. In this paper we show that using a tree topology of suitably chosen voltage regulators between the power source and loads yields higher power efficiency in the power delivery network. We formulize the problem of selecting the best set of regulators in a tree topology as a dynamic program and efficiently solve it. Experimental results demonstrate the efficacy of proposed problem formulation and solution. Categories and Subject Descriptors B.8.2 [Performance and Reliability]: Performance Analysis and Design Aides General Terms Algorithms, Design, Performance Keywords Low-power design, Power delivery network, DC-DC converter, voltage regulator