MILAN, Feb 6 (Reuters) - Utility Enel and its smaller rival Hera have won around half of the nearly 5 million customers who will exit Italy's regulated price regime for electricity at end-June without picking a free-market supplier, sources said.

Enel beat the competition in seven areas of the country, including Italy's biggest cities Rome and Milan, the body organising the auction for the liberalisation of the market said on Tuesday.

Hera was also awarded customers in seven areas of Italy, including part of the wealthy north, the so-called Single Purchaser said in a statement.

This will lead to more than 1 million new electricity customers for Hera, it said in a statement. Enel will gain around 1.5 customers, two sources said.

The two companies bid well under the base price to win the auction in the most wealthy areas of the country, data released from the Single Purchaser showed.

Italy's energy authority ARERA estimated that fixed electricity costs for customers in the new semi-regulated service could fall by around 73 euros per year.

"The electricity prices that will be charged to consumers who will end up in the semi-regulated service are so competitive -- 73 euros less per year -- that the suggestion we can give them is to stay calm, do nothing and stay where they are for the time being," said Marco Vignola, energy expert for the National Union of Consumers.

Edison won 700,000 new customers or four areas, EDF's Italian subsidiary said in a statement.

Newcomer energy supplier Illumia acquired customers in three areas of Italy. Regional utilities Iren and A2A got two areas and the Italian subsidiary of Germany's E.ON one.

The suppliers will sell electricity to the new customers under this semi-regulated framework until end-March 2027, but clients will have the opportunity to opt out and pick a free-market contract whenever they want. (Reporting by Francesca Landini and Giancarlo Navach; Editing by Ros Russell)