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 1st April to 30th 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.
Camping Plaine St Jean in Servoz also welcomes motorhomes from mid-May to mid-September. They are equipped with electricity hook-ups, sewage disposal point, washing machines and gas cannisters. There is a small grocery shop, bakery and a boucherie, plus a couple of restaurants in the village, and a pizza van (summer only) just a few minutes walk from the campsite.
For a classic camping experience, hire a retro VW combi from Champervan. All vehicles have been restored to their original 1970's glory and are fully equipped for a retro camping trip!