I'm looking to carry not more than 15kg of clothes with me from Brazil to Paris, I would like to know how the public laundry works (how should I proceed) and how much (approximately) I'll spend to wash and dry about 15kg.
Unfortunately we don't have this kind of laundry and especially where do I live we still wash it manually and hang on clothesline so even the automatic machines are not very common to see.
There are plenty of coin-operated laundries around Paris. You can find them on the yellow pages. There's always one within walking distance. Laverie is a laundry (most if not all are unmanned these days), pressing is a place where someone washes your clothes for you (mostly for things that require special handling).
Laundries are primarily coin-operated. Many but not all accept banknotes and give change. Few if any accept cards.
Typical prices are around 3–5€ for a small load, ~10€ for a 15kg load (but you surely won't have 15kg of clothes to wash all at once for a single person!), ~1€ for a run of the dryer. You can typically buy detergent as well but if you're staying around for a while buying your own from a supermarket is cheaper.
Typical opening times are something like 7–22. Often the washing machines won't start after a certain time which could be as early as 19:00 or thereabouts (it depends how good the noise insulation is and how much the neighbors complain), so if you plan to go in the evening, do make sure to check the times (“dernier lavage” means “last wash”, i.e. you must start the washing machine before that time).
Usage should be fairly simple: put your clothes and detergent in a machine, select the program, go to the payment machine, type the number of your washer/dryer and pay, then wait until done. Many but not all places have signs in English.
Don't expect dryers to leave your clothes completely dry. Use the dryers to get most of the humidity out (or don't use them in summer) and hang your clothes at home overnight to finish drying.
Parisian laundries are typically very bare-bones affairs: just the machines and a couple of chairs. If you want a drink while waiting, go to a nearby café. A few places do have wifi.
Yes you have a lot of those machines in Paris. It will cost you just few euros.
There is a website where you can find all the "laverie express" or "lavomatique" : http://lavomatic.fr/75/paris/
Enjoy!
There's a lot of those around Paris and they're simple to use even if you don't speak French. If you find yourself confused, you can always ask the staff or someone there.
It works just like a regular washing machine except it's coin operated and there's a timer. Some will offer detergent for sale but you can bring your own too. Put your stuff to wash and come back when the timer is done. I can't say it's a regular occurrence but don't be late, I once came back to find someone had piled my wet clothes on top of the machine to use it.
Temperature control isn't very precise but choosing a medium-warm wash should clean everything without the colours running.
Dryers work the same but you can keep adding time by adding coins if your clothes aren't dry enough. Make sure to check for lint, most people don't clean that.
