An Investment Services Account gives you complete control over your mutual funds- to purchase, redeem and switch funds and investment preferences at will. Keep reading! ISA is a treaty-based intergovernmental organization that aims to scale up solar energy and reduce its cost. ISA stands for International Solar Alliance, not for any other acronym. ISA is a common abbreviation that can stand for many different terms, such as Industry Standard Architecture, Individual Savings Account, or International Society of Arboriculture. See the full list of ISA definitions and categories on The Free Dictionary website. What is International Solar Alliance (ISA)? The International Solar Alliance (ISA) is an intergovernmental organization that was launched in 2015, by the Prime Minister of India and the President of France, at the United Nations Climate Change Conference held in Paris.