PVGIS is a web-based tool designed at the European Commission Joint Research Centre and can be used for evaluating the performance of on-grid and off-grid PV systems globally. The Global Solar Atlas is one of my favorite tools in this list! This atlas, which is a World Bank funded project, contains solar resources and wind resources data for the entire globe and can be used for quick estimations of system yields. SISIFO is an online design tool developed by the Solar Energy Institute of the Universidad Politecnica de Madrid and is used for the simulation of on-grid PV systems and also irrigation systems powered by PV panels.

It can also be used for component sizing and cost reduction. REopt Lite is another online tool by NREL that is used to optimize grid-connected hybrid PV systems with storage from an economic viewpoint.

SAM receives regular software updates and is great to use for university research projects. Hence, using SAM ideally requires sound knowledge of the economics of renewable energy projects and financial models. The economic and financial models in SAM are one of the most distinguising features that facilitate the decision making and project management process. SAM is used to model the technical performance of several renewable energy system and evaluate economic and financial feasibility. SAM (or System Adviser Model) is another software developed by NREL and is probably the most complex in this list. I would rate it as no.1 in this list for beginners. PVWatts (developed by the National Renewable Energy Laboratory NREL) is a great and easy-to-use online tool for estimating the energy yield of grid-connected PV systems anywhere in the world. In the following list, I have compiled 8 FREE software and online design tools for on-grid and off-grid solar systems design. If you are a renewable energy fanatic like me, a solar energy enthusiast, or a engineer trying to get quick rough estimtaes for a system you are designing, then you will almost always need to use some software.

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