Promoting Energy Alternatives is Key to Emission Reductions Act of 2021 or the PEAKER Act of 2021 This bill addresses the emissions from peaker plants and provides financial incentives for renewable energy to reduce the need for peaker plants. Peaker plants are defined as fossil fuel-fired power plants or units of power plants that are run primarily to meet peak electricity demand. In other words, peaker plants are run where there is above average energy demand, such as during extremely hot or cold weather. The bill establishes an additional investment tax credit for renewable energy generation and battery storage to replace the need for peaker plants in disadvantaged communities. In addition, the Department of Energy (DOE) must establish a grant program to provide up to $1 billion annually through FY2032 to eligible entities for clean energy projects. Specifically, grants must be awarded to assist eligible entities in carrying out (1) projects associated with the construction, installation, or acquisition of qualifying renewable energy facilities and qualifying energy storage facilities; or (2) community energy proposals or community energy studies to reduce or replace the need for peaker plants. Entities that are eligible to receive grants include state or local governments, nonprofit organizations, community-owned energy generation facilities or energy storage facilities located in disadvantaged communities, community-based energy cooperatives, or certain partnerships. DOE must also assess and report on the location of each peaker plant, the quantity and type of pollution each plant is producing, and related data as specified by the bill.