In winter it is common with frost formation in plate heat exchangers. During defrosting, the heat recovery efficiency decreases and the heat rate requirement for post-heating increases. One way to avoid frost formation is to preheat the ventilation air with geothermal energy, a so-called GeoMVHR system. This study examines the profitability of eliminating the requirement for post-heating using geothermal energy to preheat the incoming ventilation air. The study evaluates the profitability for two locations in Sweden, Stockholm and Gothenburg. The method used is the internal rate of return. The heat rate requirement for post-heating in an MVHR system without geothermal outdoor preheating and the power for operating a GeoMVHR system that eliminates the requirement for post-heating is calculated. The internal rate of return was 5.7% for Gothenburg and 5.3% for Stockholm. The conclusion was that the GeoMVHR systems could be seen as a profitable investment.