Every year, you receive your utilities bill (Nebenkostenabrechnung or Betriebskostenabrechnung). It shows how much hot water and electricity you really used. You already pay the estimated amount every month with your warm rent (Warmmiete). If you used more than you paid for, you will get an invoice. If you used less, you will get some money back.

After you move out of an apartment, the landlord will wait until the Nebenkostenabrechnung to return your deposit (Kaution).