A model for evaluating the economics of investment in Movable Interior Blankets for fuel conservation in greenhouses was developed. The after-tax costs and benefits of the blanket were analyzed using the Net Present Value method. The model uses 13 input parameters to generate an estimate of the Net Present Value of the investment for its useful life. The results of two examples are reported. Sensitivity analyses were conducted to indicate the relative importance of the various input parameters. It was shown that changes in quantitiy or quality of crop would have very large effects on net present value. At this time, there is some disagreement regarding the effect of the blanket on crop growth. Further research is needed to substantiate and quantify the potential effects on yield and quality before the effect can be usefully included in estimates of net present value. Other suggested areas of research include (1) improving the materials, design and use of the blankets, and (2) improving the ability to predict the performance of the blanket in specific greenhouses.