When one company is owned or controlled by another company, or shares the same owner or controller as another company, that company is referred to as an "affiliate". For example, when the same company owns or manages both an energy generation facility and a company that builds power plants, these two companies are affiliates of the parent company.

Management and ownership of affiliates is often limited in the energy industry, and these limits are imposed to prevent the industry from falling under monopoly control in a given region. Companies can occasionally work around these limits by creating holding companies which act as parent companies for the affiliated firms, but even holding companies have to abide by certain restrictions. In the US, ownership of energy industry affiliates is subject to the conditions of the Public Utility Holding Company Act of 1935 (PUHCA), and the activities of holding companies and their affiliates are subject to Securities and Exchange Commission (SEC) regulation and approval.

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