* Premarketing price range 1.9-2.4 euros - source
* Enel Green Power has total of 5 bln shares - source
* Retail offer on, but size not yet decided - exec
(Adds details, background, shares)
By Stephen Jewkes
MILAN, Oct 5 (Reuters) - Enel Green Power is valued at up to 12.0 billion euros ($16.5 billion) in the pre-marketing phase of the IPO being planned by its parent, Italian utility Enel SpA, a banking source said on Tuesday.
The price range for a share sale which would rank as Europe's biggest IPO this year is indicated at between 1.9 and 2.4 euros per share, the source said, though this was no more than a pre-marketing range which could change depending on investor demand.
A final price range will be issued before the launch of the IPO, scheduled for Oct. 18.
Enel, Europe's most indebted utility, hopes to raise at least 3 billion euros from the listing of a minority stake in its Green Power unit to help cut debt. That would make it the biggest IPO since Spain's Iberdrola raised 4.1 billion euros from the listing of its renewable unit in December 2007.
Enel Green Power, which has debts of around 3 billion euros, has a total of 5 billion shares, the source said. The price range indicated would give it an equity value between 9.5 billion euros and 12 billion.
Analysts of the banking consortium involved in the IPO published their research reports on Monday and a premarketing phase for the offer began.
Market watchdog Consob is expected to clear the IPO on Oct. 14 or 15. Enel management has said it could postpone the IPO if the price is not right.
Shares in EGP's main listed rivals -- Iberdrola Renovables SA, Portugal's EDP Renewables and France's EDF Energies Nouvelles -- have underperformed in the past 12 months, hit by cuts to green energy incentives in Europe and uncertainty over the U.S. climate change bill.
IPO MAIN TRACK
Enel is pursuing a dual-track process, meaning it could theoretically turn back from an IPO at the last minute should a private sale offer a higher price.
"We have still not called off the dual track approach to the sale but there is a high probability it will be an IPO," Enel Green Power Executive Vice President Roberto Deambrogio told Reuters on Tuesday.
"There will be a retail offer, though the actual amount has not been decided yet," Deambrogio added, speaking on the sidelines of a conference.
In August, a banking source who attended the launch of the Enel Green Power IPO told Reuters Enel was planning a retail offer in the region of 15 percent.
Global coordinators in the IPO are Mediobanca, Goldman Sachs , Credit Suisse and Intesa Sanpaolo unit Banca IMI, sources have said.
Bookrunners are JP Morgan, Bank of America, Morgan Stanley, Barclays, BBVA and Unicredit.
Enel shares closed up 1.6 percent at 3.887 euros while the STOXX Europe 600 Utility index was up 0.8 percent. (Editing by David Holmes) ($1=.7261 Euro)