Solar Energy Combined with Geothermal Energy Efficiency. This book and guide will lead you through the complete process of identifying, evaluating and purchasing both solar energy and geothermal power. You will be shown how combining the two sources of clean energy will provide the best return on investment. Once you understand the investment proposition you then need to identify reputable solar and geothermal companies. With a quality installation next it's time to reap the benefits of your investment. Learning the process of registering your system and grading your SRECs becomes essential...