The municipal Frankfurt energy company Mainova is initially lowering its prices for new customers in the basic supply.
The company said on Tuesday that the preliminary injunction of the Frankfurt Regional Court was to be followed.
Nevertheless, the decision is considered wrong and will be appealed against.
The energy prices would be lowered to the level that existing customers pay.
On January 3, Mainova introduced a tariff split for basic and replacement care.
The background to this is the sharp rise in energy prices, as a result of which discount suppliers in particular have stopped supplying their customers.
As a basic supplier, the city-controlled Mainova had to admit 5,000 gas customers and 7,600 electricity customers.
"Risks passed on to electricity customers"
To supply them, electricity and gas have to be purchased at comparatively high prices.
Accordingly, higher prices were initially demanded from new customers.
The company called the court decision, enforced by a competitor, "wrong".
If the legal opinion of the Frankfurt Regional Court prevails nationwide, it would be a disservice to customers, argued Mainova.
"Because this means that the risks associated with the short-term business models of the energy discounters are shifted onto the shoulders of all customers in the basic supply." The prospects are also good because of the different decisions of the regional courts in Berlin, Leipzig and Cologne.