In Germany, service costs are always (§ 107, 3.) included in the compensation. But it’s common to give a tip if you are happy with the service (but you are never required to). If you are unhappy with the service, you should give no tip at all (instead of a very low tip).
I found the following recommendations (sources are in German):
knigge.de, Der Trinkgeld-Knigge (here and here also): for upscale hotels:
- room service: 2-5 € per delivery
- luggage carrier: 2 € per item
- concierge (for special services, e.g., organizing tickets for a sold out event): 10 €
spiegel.de, Trinkgeld-Knigge: Man sollte, aber muss nicht:
- how much to tip depends on how long you stay, hotel price range, and of course how much money you have
- it’s uncommon to round up the hotel bill at checkout
- always tip the luggage carrier and the room attendant
- you may leave the tip in your room (e.g., in the ashtray or on the nightstand); to make clear that it’s a tip (and that you didn’t forget your money there), you may leave a thank you note
- to make sure that the whole service staff gets a tip, you can give a summed up tip at the reception before checkout
experto.de, Rainer Wälde: Trinkgeld geben - aber mit Stil:
- valet parking: 1-3 €
- porter (for calling a taxi; for helping to get into the taxi): 1 €
- luggage carrier (often also the porter): 1 € per heavy item
- if you pay a restaurant/bar bill at the checkout, don’t forget to add a tip: 5-10%
- concierge (for special services, e.g., organizing tickets/presents): 1-3 €
- houskeeper: before checkout, leave a tip in the bathroom or at the nightstand
- houskeeper (for bringing additonal pillows, cosmetics, a vase, etc.): 1 €
berlin.de, Trinkgeld: tips for hotels in Berlin:
- luggage carrier: 1-2 € per item
- housekeeping: 2-3 € per day
- concierge (for special services): 5-10 €
faz.de, Das „Danke“ gehört dazu :
- luggage carrier: 1 € per heavy item
- in general, you should say "thank you" when giving a tip (so don’t leave it on the table in the restaurant; don’t hand it over wordlessly); only for the housekeeping team it’s okay to leave it in your room (e.g., on the table or on the bed)
- tip valet parking service, porter, concierge/reception and housekeeping separately
test.de, So geben Sie im Urlaub richtig Trinkgeld
- luggage carrier: 1 € per item
- housekeeping: 1-2 € per day (leave it on the nightstand)