FRANKFURT (Reuters) - RWE's (>> RWE AG) renewables and power distribution subsidiary Innogy is ready to make heavy investments in its power grids, the Chief Executive of Germany's second biggest energy utility told investors on Thursday, as it prepares to list shares in the newly-named unit by the end of the year.

RWE last year unveiled the plans to separate its renewable power generation, distribution and retail businesses from its troubled thermal and nuclear power generation operations, which have been hit by Germany's drive to develop more renewable power capacity at the expense of coal and gas-fired plants and to close all its nuclear stations.

The exact size of the Innogy listing will depend on market conditions but could exceed a minimum of 10 percent that RWE has defined, Chief Executive Peter Terium said.

Innogy has plans to invest between 6 and 7 billion euros (5-5.79 billion pound) between 2016 and 2018, mainly in its grids, he said, as old equipment needs to be made fit for the digitalised nature of energy generation and usage of the future.

RWE is targeting a dividend payout ratio of between 70 and 80 percent, anticipating payment of a full dividend for 2016, he added.

Overhauling its ailing RWE npower UK retail business, one of Innogy's core Eurupean markets, was also on track, as RWE managers are geared to tackle problems with IT and billing systems which had led to a mass customer defection there last year.

The ongoing energy sector transformation would lead to business opportunities some of which were not even apparent, Terium said.

"The key to succeed in this environment is flexibility and speed to adapt," Terium said, citing partnerships with international energy service companies.

Analysts expect the sale of 10 percent of Innogy to bring in about 2 billion euros, which would give the entity a market value of 20 billion, nearly three times that of RWE now.

The name Innogy, unveiled on Wednesday and to be deployed from September onwards, is the same as RWE's former renewables unit but now also embraces its grid, infrastructure and retail activities.

RWE's move follows in the footsteps of larger rival E.ON (>> E.ON SE), which has spun off its conventional power business into a separate entity called Uniper.

RWE shares extended gains and were up 5 percent at 14 euros by 1132 GMT, as RWE's Capital Markets Day of presentations continued in London.

(Reporting by Vera Eckert; Editing by Jonathan Gould and Greg Mahlich)

Stocks treated in this article : RWE AG, E.ON SE