While grid-scale electrical storage remains impractical, behind-the-meter storage systems show promise, offering greater flexibility to be dynamically controlled either individually or in aggregate. Thermal loads account for the largest share of final energy consumption in residential buildings. Small-scale Thermal Energy Storage (TES) provides many benefits and can serve as a viable alternative to reduce battery storage size. In this paper, we investigated the integration of a fully stratified, water-based TES tank with a residential-scale secondary loop system that provides both cooling and heating. We compared two TES configurations: an Above-Ground TES (AGTES) tank and an Underground TES (UGTES) tank. Case studies focused on Stillwater, Oklahoma and Chicago, Illinois examined the effects of adding the TES on overall performance of the Heating Ventilating and Air Conditioning (HVAC) system and electricity costs. Results indicate that for a 132 m2 building in both locations, a 1900-l tank can effectively shift peak hours thermal loads to off-peak hours. Moreover, the addition of TES can slightly improve performance and reduce electricity costs for cooling by up to nearly 55% and 60% for Stillwater and Chicago, respectively. For heating, though, little savings in performance and cost are possible with currently available rate structures. Parametric studies presented here provide insights into the impact of three tank design parameters: tank size, insulation thickness, and tank burial depth.