Free for SWK customers - your SWK Card App. The SWK-Card is the free customer card of your regional energy service provider, the STADTWERKE KREFELD AG, SWK for short. Anyone who has the SWK card can use price advantages from the associated advantage partners. Whether leisure, culture, musicals, sports or shopping: Anyone who has the SWK Card can save money - for themselves and the whole family! Visit for example the Movie Park Germany, the Fort Fun Abenteuerland or Efteling. With the SWK-Card