My ISP = Comcast. I’ve been renting a cable modem from them for years. Tired of renting it, would like to buy one.
Will any ol’ cable modem I find available on Pricegrabber do the job? Or are there specific features/specs that will render any given modem compatible/incompatible with Comcast?
Comcast’s list of acceptable devices
Don’t forget to call them once you install it and register its MAC address.
If you are already using Comcast’s digital phone, you already have a Comcast cable modem.
I am not using Comcast’s digital phone.
Despite not using Comcast’s digital phone, I do have a Comcast cable modem already because I use Comcast for internet access. The mere having of a modem isn’t the issue: As noted in the OP, it’s renting vs. owning.
ZipperJJ, thanks for the link; that’ll do nicely.
Make sure it’s DOCSIS3 compatible. Most cable operators have probably upgraded by now and modem makers probably only make this type now, but if you go for a used modem, definitely check.
You shuld speak with tech support. They will let you know which modems are compatible.
If I may ask, why do you want to own it instead?
Will CC even knock anything off your bill if you do? Even so, I can’t imagine it being that much. Plus, if you ever have any issues and call tech support I’ll bet once they know its your modem they won’t lift a finger to help you.
I’m not the OP, but know what s/he’s thinking. I purchased a cable internet modem from the get-go when I switched to cable. I have RCN (and love them), and they would have charged me $5 a month for modem rental. That $5 a month is part of their advertised price, so it looks like a discount on my bill. Instead of $35 a month, I pay $30. My 3.0 modem cost me $80, so I only have to use it for 16 months to break even, and every month after that is $5 saved x however many months/years it lasts after that. It makes total sense.
If I’ve needed a modem reset or something, it’s never been a problem that it’s not theirs. If it fries and burns, of course that’s my problem and risk.
if it’s compatible, pretty much any old modem will work. I’ve been using the same modem (my own) with Comcast for nearly eight years now. I’m not aware of any “new features” with newer modems, I think they’re pretty much a “solved” appliance at this point.
Now routers, though, there you should do some research 
Working cable modems are dime a dozen on eBay. I don’t think there is a greater new vs used price spread between retail and eBay for any other electronic device. The reason you can get them so cheap is that people dump modems as they move to addresses that require a different broadband interface. Price shop before you buy. I’ve found Motorola modems to be very reliable.
Newer modems are DOCSIS 3.0 and allow bonding of mutiple channels for higher bandwidth, if supported by the ISP.
Just buy this one. It works great with Comcast:
Motorola Surfboard SB5100 Cable Modem - $32 on Amazon (used)
Wow, my OP must be hard to read.
I am currently renting my cable modem from Comcast, where renting = “paying them a monthy fee for the use of their.”
Like SeaDragonTattoo, Comcast is charging me $5 a month for the privilege of using a cable modem they have provided me; this charge is a line item on my monthly cable bill from them. I’m expecting to stick with them for the foreseeable future, so it makes economic sense to purchase one and lower my monthly bill by $5.
njtt, thanks for the link; those quotes were a riot.
The best thing about owning your cable modem, is that if it dies you simply go buy a new one. Or if you think it’s dying or causing problems, you can buy a new one to test out. You don’t need to wait 3 days for a tech to come install one or take off work to go to the Comcast center during its weird hours.
I’m the go-to guy for any computer stuff for my friends & family and its just that buying my own cable modem was never something I wanted to do. Not to sound snobbish but I always find that those kind of small, long-term accrued savings never get noticed (by me anyway!).
And I too have never had much problems with a cable modem. But when I first got high speed with Verizon DSL, whenever I called them and mentioned that I had it connected to a router they always immediately started in with, “Oh we don’t support home networks of any kind, you’ll have to unhook that first- blah blah…” so I quickly learned to never mention that. The same thing would happen when I called the cablevision people and mentioned that I had a TiVo, they would practically hang-up on me!
And its kind of like buying your own TV cablebox. You can, but I always felt that that hardware is just too intrinsically linked to the rest of their hardware to not be able to 100% guarantee it won’t someday cause problems.
Comcast just went up to $7 a month for my modem. Thank you for finally forcing me to buy one, Comcast! I ordered a new SB5101 from Amazon for $55.
Except DOCSIS is an actual, real-world standard that is documented and written down and everything, right? It isn’t ‘Verizon’s DOCSIS by Motorola’ or ‘Comcast’s DOCSIS+Cherries’, after all. So are any cable ISPs actually known to not implement DOCSIS correctly?