There is a need for stakeholders in the construction sector to evaluate energy efficiency and renewable energy generation alternatives appliable to buildings at early design stages. In this regard, public and private organizations have developed tools to compare different options. It was observed that when the objective was to create nearly Zero Energy Buildings (nZEB), the number of tools was still scarce. With this aim, this work presents a new, free digital tool that can predict, among others, energy consumption, energy generation, emissions savings, and payback time. For this purpose, different alternatives applicable to the roof, such as phase change material (PCM), insulation, and reflective paint, as well as to window-to-wall ratios (WWR), with four different glass technologies, can be evaluated. Furthermore, four renewable energy systems were available for comparison: the solar thermal collector (ST), photovoltaic (PV), flat hybrid solar collector (PVT), and low-concentration parabolic solar collector (LCPVT). Our tool was developed based on the results of transient dynamic building simulations of both residential and non-residential building models located in the hot semi-arid conditions of Monterrey, Mexico. Among the results, the small impact of using only reflective paint, the need to combine PCM with insulating material to obtain the best energy savings, and the large impact on emissions savings when using an LCPVT stand out.