New XPS15 (L501X) AC Adpater

The AC adapter which came with the new xps 15 is a 130W source, however dell suggests buying a 90W ac adapter (in the part upgrade section) as a replacement. I would like to get a second AC adpater, but i do not believe a 90W source will be sufficient. The current adapter (130W) gets pretty warm from use which makes me believe a 90W adapter wouldnt be able to handle the load. When ordering the laptop, i thought it was strange that i couldnt buy a second adapter along with my order (under the accessories options). Has anyone used the 90W adapter with the new xps15? Does it power the laptop and charge the battery? Are there any other alternatives out there?

Thanks