In this paper we introduce a model and an optimization methodology for terrestrial solar thermoelectric generators (STEGs). We describe, discuss, and justify the necessary constraints on the STEG geometry that make the STEG optimization independent of individual dimensions. A simplified model shows that the thermoelectric elements in STEGs can be scaled in size without affecting the overall performance of the device, even when the properties of the thermoelectric material and the solar absorber are temperature-dependent. Consequently, the amount of thermoelectric material can be minimized to be only a negligible fraction of the total system cost. As an example, a Bi2Te3-based STEG is optimized for rooftop power generation. Peak efficiency is predicted to be 5% at the standard spectrum AM1.5G, with the thermoelectric material cost below 0.05 $/W-p. Integrating STEGs into solar hot water systems for cogeneration adds electricity at minimal extra cost. In such cogeneration systems the electric current can be adjusted throughout the day to favor either electricity or hot water production. (C) 2012 Elsevier Ltd. All rights reserved.