We describe an approach to optimally schedule the charging of groups of electrical storage heaters to minimize energy-procurement costs. Our control is based on smart meter infrastructure augmented with simple control logic to enable the time-shifted charging of electrical heaters. We derive a thermal model to predict the daily energy need of a house and also a model to approximate the power consumption behavior of groups of heaters. Further, it is shown how the computation of the minimum-cost charging schedule with respect to given energy prices can be formulated as a constrained integer linear program. We provide initial results obtained from applying our approach to real installations in southern Germany.