(Adds detail from statement, Alpiq share move)
ZURICH, April 5 (Reuters) - Swiss investors EOS Holding and Primeo Energie are jointly buying French group EDF's 25 percent stake in utility Alpiq Holding for 489 million Swiss francs ($489 million), or 70 francs per share, the companies said on Friday.
The move by the two minority shareholders aims to consolidate control of Alpiq in Swiss hands and eventually take the power supplier private, they said in a statement.
The stock gained more than 11 percent in early trading and was up 8.1 percent at 70.50 francs by 0815 GMT.
ZKB analyst Sven Bucher said the pace and pricing of the purchase from EDF were surprising as he had thought EDF would demand a higher price.
"Alpiq has an opt-out clause so no mandatory offer or minimum price is required but we assume expectations of a price higher than the current one will boost the shares," he said in a research note before the market opened.
The transaction will be financed through mandatory exchangeable loans from CSA Energy Infrastructure Switzerland, a fund managed by Credit Suisse Energy Infrastructure Partners.
EOS until now had 31.4 percent of Alpiq and Primeo Energie had 13.7 percent. The EDF deal will boost the Swiss consortium's combined Alpiq stake to 88 percent.
The transaction is set to close in the first half of 2019, subject to approval by German competition authorities.
Alpiq accounts for 15-20 percent of Switzerland's power output. It plans to focus on hydropower as Switzerland exits nuclear energy production.
$1 = 0.9995 Swiss francs Reporting by Michael Shields, Editing by John Revill and Dale Hudson