Green-Y offers a low-cost electricity storage and provides renewable heating and cooling. The combination allows to significantly reduce the costs and offer an already today highly proftable residential electricity storage with an amortization period below 5 years. Besides this, the eco-friendliness is given by using only air and water as working fluids. The solution follows a modular approach and is scalable from a decentral application at a family house up to an application for an utility.