Geothermal heat pump (GHP) systems are known for their higher energy efficiency, lower maintenance, and lower environmental impact compared to conventional heating systems, but their disadvantage is higher capital cost. The objective of this study is to examine the feasibility of greenhouse heating with GHP systems. Both closed- and open-loop systems are examined at four locations across the U.S. and a net present value analysis is conducted for a 20-year life-cycle for various GHP base-load fractions. Results show that it is only under situations of relatively low geothermal loop installation costs and/or relatively high natural gas costs that some portion of a greenhouse could be economically heated with a closed-loop GHP system. Open-loop GHP systems show considerably more favorable economics than closed-loop systems. Of course, open-loop systems would need to be sited at locations with sufficient ground water supply.