Abstract
The objective of this study is to evaluate economically the passive solar heating system. Data collected from tomato greenhouses in the Agriculture Research Center of Northern Greece was analyzed. For Comparison, two other conventional heating systems were used: the traditional anti-frost system and the diesel-fired furnace system. Models have been constructed to assess each heating method and several approaches of appraisal such as net present value, internal rate of return, benefit/cost ratio and payback period were measured in order to fulfill the assessment. The importance of the passive solar system was revealed not only as an energy-saving method but also as a significant contributor to farmer's income and an appropriate system avoiding the risk of high initial investment, which is generally associated with unconventional systems. Meanwhile, it was indicated that the diesel-fired furnace system is ineffective compared to the passive solar system, this ineffectiveness is particularly due to its high fuel consumption and relatively high initial investment. Finally, sensitivity analysis highlighted the importance of the product price in affecting benefits and indicating that income will increase dramatically with earlier production.