A method for feeding electrical power at a network connection point into an electrical supply network by at least one wind power installation includes generating electrical power from wind, feeding the generated electrical power or a portion thereof into the electrical supply network, offering an instantaneous reserve for additionally feeding or reducing the feeding into the electrical supply network in order to support the electrical supply network, and additionally feeding electrical power or reducing the fed-in power up to the offered instantaneous reserve, depending on a network property and/or an external requirement. The method is operative to support the electrical supply network. A reserve level of the offered instantaneous reserve is settable as an offer level.