The Wall Street Journal reported.
"E.ON employees have made it clear that they are prepared to fight for wage increases," Verdi board member Erhard Ott said.
He also criticized the management's offer for a 1.7-percent pay rise and described it as "unreasonable".
German labor unions have demanded a 6.5% increase in pay, and better hiring conditions.
Ott said that the open-ended strike will affect E.ON's power generation operations, but the will still be able to get heating as it would not be cut off.
E.ON said it hoped to resume negotiations ahead of the strike.
"We hope very much to return to the bargaining table before the start of a possible strike to achieve a compromise that is acceptable to both sides," E.ON board member Regine Stachelhaus said in a statement.
She added that E.ON, in principle, is prepared to compromise, and will do everything to avoid any disruption to the supply of energy to customers and consumers.
German labor unions ver.di und IG BCE have said a substantial majority of members have voted in favor of a strike at the country’s biggest power supplier, E.ON AG, in a bitter wage battle.
The unions said on Friday that in a strike ballot held earlier this week, 91.4 percent of its members voted for walkouts from February 4,