Which country? You generally have to size per the applicable code. Kitchens and restaurants are separate considerations.

Realistic average consumption should depend on location of the hotel. You need data for this. What is the average consumption for hotels in that locality? This should guide you. If you cant get this data, then you should be looking at other data like population around the locality, tourist attraction and so on. However, note that if you design with this average in mind, there will always be one day when a hotel will be fully booked and all appliances running at their full capacity. Imagine the hotel is booked by campers or people who are all attending the same event at the same time. So expect all heaters or ACs to start and run almost at the same time and so on. If fund in not a very serious constraint, design at 100% capacity (essentially about 120%), otherwise, you should not go anything below 80%.

thanks for your help. it is for Indonesia and luxury hotel, it is possible to have full capacity of course. but i was thinking ,even at full capacity, AC compressor will never run all at once, water heater same , ect So i calculate with 70 %...oupss

Yeah you are right, But i will rather go with 80%.

thanks a lot