Greenhouses are hit hard by rising energy costs, with some studies reporting that heating is upwards of 70% of greenhouse energy consumption. Due to the rising cost of heating, as well as increasing demand for renewable sources of energy, alternative options are being considered. This analysis compares the 15-year cost of a solar-assisted ground source heat pump system to a conventional high-efficiency hot water boiler system in a mid-Michigan greenhouse, including the initial investment, operational costs and maintenance costs. Included are the net present value of costs for each system, discussions on the amount of energy purchased compared to the total amount of energy consumed, how changing the inputs will affect the results of the study, and a discussion on the effect of a carbon tax. Initial results indicate that the average annual cost per square foot of the solar-assisted geothermal heat pump system is larger than that of the conventional boiler system while the average energy costs per square foot are smaller for the heat pump system.