Wireless localization systems based on determination of signal runtime (TOA/TDOA) are of great importance for a variety of applications. In many cases, synchronization of the clocks of the agent nodes to those of the network nodes (anchors) has to be performed together with the localization. The current paper investigates the fundamental accuracy limits of such a joint localization/synchronization. In particular we analyze the impact of allocating power to the different anchor nodes, and optimize this power allocation to maximize accuracy. Simulation results confirm the importance of proper power allocation; known special cases (TDOA localization, localization with already-synchronized clocks) are recovered from our general solution.