A buried pipe heat transfer model was developed and implemented within the EnergyPlus simulation program. A literature review revealed different solutions attempted for this problem, including analytic methods, finite difference solutions, and transfer function methods. Three separate models: a modified earth tube model, a fully radial finite difference model, and a mixed-coordinate finite difference model were tested against a robust verification model developed in Fluent. Fluent was used due to its ease of setting boundary conditions and developing a sufficient mesh. The earth tube model is currently implemented in EnergyPlus, and was tested both as an earth tube and a pipe. The model's extreme simplicity led to poor tests upon verification. The radial model encountered significant stability problems due to the explicit formulation of the model. The mixed-coordinate model proved the most stable and accurate of the finite difference models. Although transfer function methods were investigated, they were not selected due to convergence problems in thick soil. In addition to verification against the Fluent model, the models were tested under high flow rate testing which removes axial heat transfer, and constant pipe wall testing. After implementation and testing in VBA, the mixed-coordinate system model was selected for implementation in EnergyPlus. This model utilizes a radial coordinate system in the near pipe region, with a coarse Cartesian system throughout the rest of the domain. The finite difference update equations are implicitly derived. At each cross section, 2D heat transfer is modeled, neglecting axial heat transfer. The far-field boundary is a function of time of year and ground depth based on known surface temperature data. The initial implementation in VBA agreed to the verification model with an annual RMS error of 1.72°C on the exiting fluid temperature. The final implementation in EnergyPlus agreed to the VBA implementation to within 0.12°C. This small deviation is related to the time step management difference between the two implementations. This model is currently implemented in the plant manager of EnergyPlus, and is available to better predict heat gains and losses in the ground for all buried pipes.