Why do power outages affect Comcast's internet service?

I assume their nodes are redundant, but your modem likely isn't, unless you have an eMTA which are generally only in play if you have a voice service through Comcast. 

Comcast's equipment relies on the local power grid to function. Each node, switch, hub is tied into the (local) power grid, just as your house or apartment is. If the power grid has fluctuations (brown outs) or stops receiving power [from the regional grid](black out) for what ever reason, their equipment stops functioning. Period. No Internet, telephone or tv. 

Their nodes are most definitely not redundant. I have been having the same problems, over, and over, and over, and over, and over, with the node that I connect to for the past 5 years. I've had over 4 dozen service calls to my address and the issue is still not resolved. 

yes, see this previous post where i voiced my concerns about this

http://forums.businesshelp.comcast.com/t5/Connectivity/Comcast-Goes-out-when-Power-Does-I-have-a-generator/m-p/15456

as far as i can tell, your modem goes offline because a local neighborhood amp or node's battery backup has failed, as ordinarily i believe these devices do have batteries; i would highly assume that the head-end has batter backup power (and would be quite worried if it didn't.)

But in any case for "business class" service, one would think that at least SOME level of power redundancy would on Comcast's network (even if it's just for 20-30minutes worth of time). I realize things like batteries fail from time to time, and that Comcast can't be on top of EVERY piece of equipment, but stil....

What would be great is if there was a way for customers to report this kind of information.

Hey train_wreck, what it is....

I think it is fair to presume that Comcast should have power related backup capability for its Nodes, etc. I am sure that all Nodes do have their inherent power supply failover, as well as, intrinsic redundant failover for other electronic modules contained within.  

However, whenever there are any catestrophic inclement conditions or someone smashes into and take out telephone pole from power companies, Comcast is subject to the same dependent mercy that every residential, SMB, national, and enterprise  customers are subjected to open power circuits, amps, etc. For this reason, Comcast does not have it own built-in power generators at every single node because it would actually not make sense in light of open power circuits defeating the purpose. However, it does have built-in power generators at its plant engineering facilities that handle many of the Head-End Nodes equipment control factors, but again, if there is an open power circuit stopping power distribution then Comcast must await for the power company to do whatever is necessary to close the circuit for power distribution availability.

I can assure you that Comcast is ALWAYS right on top of ANY outages negatively impacting Comcast services from being up and running for ALL customers. Comcast has 24 hour serviceability and maintainability for any and all outages at all time.  Comcast is always improving their technology, service capability, etc. In order to facilitate this, it is necessary to usually accomplish this typically between 1:00 AM to 6:00 AM, when most users are not in dreamland.  

So, I hope this sheds some reasonable light on Comcast being subject to the same power open circuit outages as everyone else.