Xfinity Data Usage and Xfinitywifi

So Comcast/Xfinity has for a while been piggy backing their xfinitywifi service on top of their customers service by configuring their leased routers to broadcast the signal. Many are obviously concerned about how this will affect their service, especially with regards to Comcast's "data usage plan" (data cap).

Claims around the internet vary as to whether or not data used by the xfinitywifi access point count toward the customers data usage. Many people have posted about suspiciously high usage and assume it must be caused by people using the wifi. Others claim it counts against the person who is using it since to use the access point one needs to first log in using an xfinity account with an internet service plan. Yet others claim that the data is essentially free claiming it does not count toward either party's usage.

Comcast themselves make conflicting claims. In their FAQ they claim usage is associated with the visitors account.

Does the new Home Hotspot impact my Internet speeds or data usage?
Also, the usage and activities of visiting users are associated with the visitors’ accounts and therefore do not impact the homeowner.

On their support page they claim it does not count toward the visitors account.

Will the homeowner be accountable for visitors' activities and data usage on the wireless gateway?
No. The homeowner is not accountable for visitors' activities and data usage. Visitors are accountable for their own usage based on their XFINITY WiFi Hotspot eligibility. For example, if the visitor is a qualifying XFINITY Internet subscriber, their Home Hotspot usage will not count toward monthly usage allowances. If the visitor is not a qualifying XFINITY Internet subscriber and/or not a Comcast customer, the XFINITY WiFi Hotspot eligibility rules apply.

So what's the deal?

A recent experience had me questioning the claim that data usage is counted against the account connecting to the wifi. As such I decided to test this claim myself by using a nearby xfinity wifi source for my internet for a few days and track my usage during that time.

I run OpenWRT on my router along with vnstat to track usage in near real time down to the byte for each interface. During this test I disabled my modem connection and configured the router to connect to xfinitywifi. I then reset my traffic counter for the wlan0 interface which corresponds to the xfinitywifi connection.

The results

Starting on August 1st I made the changes to switch to xfinitywifi and reset the local traffic counter. At this point my local counter for my modem connection was at 8.48GB and xfinity's usage meter showed 7GB. Xfinity states that their meter may be off by 24-hours so the difference could be accounted for by that delay.

VNStat's usage meter on 2016-08-01: 8.48GB

Xfinity's usage meter on 2016-08-01: 6GB

I checked my usage meters again on the 3rd to see what had changed. Xfinity's meter had reached 9GB which puts it even (assuming rounding up) with what my router showed for usage on the 1st before the switch to the wifi. My local meter had gone up another 37.3GB during that same time frame. So far this is unaccounted for.

VNStat's usage meter on 2016-08-03: 37.308GB

Xfinity's usage meter on 2016-08-03: 9GB

I check again on the 4th to see if any of that previous usage had been accounted for or not yet. My local meter had gone up again to 59.1GB but the xfinity meter still showed only 9GB used.

VNStat's usage meter on 2016-08-04: 59.178GB

Xfinity's usage meter on 2016-08-04: 9GB

Seems pretty clear to me that the usage while on their wifi is not being attributed to my account. Now whether or not this was counted against the person hosting the wifi I cannot say, I do not know who around here was providing it.

As of writing this, it appears the wifi usage has still not been tied to my account. My router is currently showing 60.3GB while xfinity shows 59GB.

VNStat's usage meter on 2016-08-07: 59.178GB

Xfinity's usage meter on 2016-08-07: 9GB