energies Review Solar Energy in the United States: Development, Challenges and Future Prospects Sanzana Tabassum 1 , Tanvin Rahman 2 , Ashraf Ul Islam 2 , Sumayya Rahman 2 , Debopriya Roy Dipta 2 , Shidhartho Roy 2 , Naeem Mohammad 2 , Nafiu Nawar 2 and Eklas Hossain 3, *   Citation: Tabassum, S.; Rahman, T.; Islam, A.U.; Rahman, S.; Dipta, D.R.; Roy, S.; Mohammad, N.; Nawar, N.; Hossain, E. Solar Energy in the United States: Development, Challenges, and Future Prospects. Energies 2021, 14, 8142. https:// doi.org/10.3390/en14238142 Academic Editor: Bashir A. Arima Received: 6 November 2021 Accepted: 30 November 2021 Published: 4 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Electrical and Electronic Engineering, Islamic University of Technology, Gazipur 1704, Bangladesh; sanzanatabassum@iut-dhaka.edu 2 Department of Electrical and Electronic Engineering, Khulna University of Engineering and Technology, Khulna 9203, Bangladesh; tanvinrahman9728@gmail.com (T.R.); ashraf.islam.284@gmail.com (A.U.I.); sumayyar1999@gmail.com (S.R.); roydebopriya54@gmail.com (D.R.D.); swapno15roy@gmail.com (S.R.); nmsami36@gmail.com (N.M.); nafiu.nawar@gmail.com (N.N.) 3 Department of Electrical Engineering & Renewable Energy, Oregon Tech, Klamath Falls, OR 97601, USA * Correspondence: eklas.hossain@oit.edu Abstract: The ambitious target of net-zero emission by 2050 has been aggressively driving the renewable energy sector in many countries. Leading the race of renewable energy sources is solar energy, the fastest growing energy source at present. The solar industry has witnessed more growth in the last decade than it has in the past 40 years, owing to its technological advancements, plummeting costs, and lucrative incentives. The United States is one of the largest producers of solar power in the world and has been a pioneer in solar adoption, with major projects across different technologies, mainly photovoltaic, concentrated solar power, and solar heating and cooling, but is expanding towards floating PV, solar combined with storage, and hybrid power plants. Although the United States has tremendous potential for exploiting solar resources, there is a scarcity of research that details the U.S. solar energy scenario. This paper provides a comprehensive review of solar energy in the U.S., highlighting the drivers of the solar industry in terms of technology, financial incentives, and strategies to overcome challenges. It also discusses the prospects of the future solar market based on extensive background research and the latest statistics. In addition, the paper categorizes the U.S. states into five tiers based on their solar prospects calculated using analytical hierarchy process and regression analysis. The price of solar technologies in the U.S. is also predicted up to 2031 using Wright’s law, which projected a 77% reduction in the next decade. Keywords: solar energy; United States; photovoltaic vs. concentrated solar power; challenges; future prospects 1. Introduction The transition from fossil fuels to renewable energy (RE) has gathered significant momentum over the past decade. Due to the expanding industrialization and growing population, the global energy demand is expected to continue to increase by 50% between 2018 and 2050 [1]. This soaring demand is being matched by the increased combustion of fossil fuels, which still dominate the energy mix and come with drawbacks, such as depleting reserves, increasing prices due to carbon tax, emission of harmful by-products, such as CO 2 , NO x , SO 2 , and mercury, and the failure to limit the global temperature rise under the 2 ◦ C target of the Paris Agreement [2]. The decarbonization of the electricity mix, and all energy systems as a whole, necessitates shifting towards cleaner, sustainable, and renewable energy sources (RES) that are pioneering eco-friendly energy solutions. Leading the RE race is solar energy, which is the fastest growing electricity source at present [3]. In a single hour, the amount of the sun’s energy that reaches the Earth exceeds the entire world’s consumption in a year, making it a lucrative source of energy to tap into [4]. With Energies 2021, 14, 8142. https://doi.org/10.3390/en14238142 https://www.mdpi.com/journal/energies