"If we expand quickly, we can make it by spring 2025. The supply problems might be somewhat manageable a year earlier," Markus Krebber told Frankfurter Allgemeine Sonntagszeitung.
He said apart from building infrastructure to import liquefied natural gas, this also required building new transport pipelines across European countries.
German Economy Minister Robert Habeck has previously said the country could manage without Russian gas supplies by as soon as mid-2024.
RWE's commodity exposure to Russia includes 15 terawatt hours (TWh) of gas deliveries by 2023, which it has reduced to 4 TWh since Russia began its invasion of Ukraine - action Moscow calls a "special military operation".
Asked about future Russian gas supplies, which are subject to a new payment mechanism that has led to concerns about disruptions, Krebber said: "I expect a further shortage of gas supplies and not that someone will turn off the gas tap completely."
(Reporting by Christoph Steitz; Editing by Mark Potter)