Unipro currently has a market value of 97.26 billion roubles ($1.31 billion).
The markdown was due "to the great uncertainty about an actually achievable and enforceable selling price", the company said in emailed comments after releasing full-year results.
Uniper earlier said it practically no longer had control over Unipro, in which it owns 83.7%, and that it now reports the division under discontinued operations.
($1 = 74.4500 roubles)
(Reporting by Christoph Steitz, Vera Eckert and Tom Kaeckenhoff; Editing by Miranda Murray)