SAO PAULO, Jan 22 (Reuters) - Brazilian power firm Energisa has launched a follow-on share offering aimed at raising around 2 billion reais ($405.60 million) to strengthen its capital structure, according to a Saturday securities filing.

The company will issue 78.3 million new common shares and 121.97 million preferred shares as part of the offering, it said, but that could be increased by up to 25% depending on demand.

Based on Energisa's Jan. 18 closing price of 49.99 reais per unit, the offering would raise up to 2.5 billion reais if the overallotment is sold.

Pricing of the offer is scheduled for Jan. 29.

Itau BBA, Bank of America, Bradesco BBI, BTG Pactual, Citi, JPMorgan, Santander and Scotiabank Brasil will manage the offering.

($1 = 4.9310 reais) (Reporting by Peter Frontini and Leticia Fucuchima; Editing by Steven Grattan)