Motorhomes
There is only one official parking spot for camper vans and motorhomes in Chamonix town; located at the Grepon car park next to the Aiguille du Midi you'll find access to a 'Flot Bleu', for sewage removal, water and an electricity socket.
In Les Houches you can park your caravan at a dedicated "aire de camping-car" on Route du Pont, equipped with a service area, RV dump, water supply, electricity hook-ups and WiFi. The site offers 22 parking spaces on one acre of sunny land with cracking Alpine views. Entry to the campsite is via an unmanned automated tollgate where first-time visitors gain access by payment (credit/debit card). The campsite is open 24/7 from April to November.
There is an over night unofficial motorhome spot located on Route du Bouchet, just past the MBC bar. You can park over night but there is no access to a 'Flot Bleu' for sewage removal, water or electricity so you will have to move on quite quickly either to the Grepon car park or to a proper camp site.