5 Best Xfinity-Compatible Modems

After comparing compatibility, user satisfaction, DOCSIS technology, and max wired connection speeds, we recommend the Motorola MB7621 as the best cable modem for most Comcast Xfinity plans.

We’re longtime renters of the Xfinity xFi Gateway modem and router, but the idea of saving money by buying our own wireless router pushed us to research dozens of cable modems. The xFi Gateway rental fee is $14 a month, which means you’ll potentially save $168 a year if you buy your own modem. (And router too, of course.)

Here’s how each one of these Xfinity-ready internet modems stacked up under our scrutiny.

Ready to swap your Xfinity modem out with one of your own? It’s a great way to put that equipment rental fee back in your pocket, so we don’t blame you.

But before you go out and buy your new cable modem, here’s what you should know.

Most importantly, make sure your potential new cable modem is compatible with your Xfinity internet service.

Xfinity lets you do this online with an easily searchable database of all supported modems. (You’ll need to provide your service address and internet plan speed to get access.)

DOCSIS, or Data Over Cable Service Interface Specification, is the technology that handles the transfer of data between your internet provider and your computer.

DOCSIS 3.1 is the latest version of this technology, but not all internet providers support it. If you’re eyeing a DOCSIS 3.1 cable modem that’s not backward compatible with DOCSIS 3.0, you’ll need to check with your internet service provider (ISP) to make sure it supports DOCSIS 3.1 tech.

But for now, DOCSIS 3.0 is still common and works just fine.

Channel bonding tells you how many channels a modem has for downloading and uploading data. Think of it like lanes on a highway: The more lanes, or channels, that you have, the more traffic, or data, that can get through.

When talking about channel bonding, the first number refers to the number of channels available for downloading data. The second number refers to how many channels are available for uploading data.

For example, a cable modem with 8x4 channel bonding features eight download channels and four upload channels. This modem should support an internet plan with up to 100 Mbps download speeds.6

More channels means faster speeds—but you’ll probably pay extra for them. So look for a modem with just enough channel bonding to support the internet speed advertised in your plan. You shouldn’t need more than that.

Your Xfinity internet plan comes with a promised maximum download speed. For example, the Performance Select plan comes with a promised max speed of 100 Mbps.

Another way to check what speed your internet plan comes with is to run a speed test. This gives you a more accurate view of what speeds you actually get. We recommend running several speed tests over the course of the day to get a bigger picture of how much your speed fluctuates at different times.

You’ll want to keep this max speed in mind when searching for a cable modem. If you buy a modem that doesn’t support your max speed, you’ll essentially waste money by paying for speeds you can’t get.

The Motorola MB7621 is an Xfinity-certified cable modem that comes with wired internet connection speeds of up to 1,000 Mbps.¹ That covers pretty much every single Xfinity internet plan (aside from its extremely limited 2,000 Mbps plan).

At about 8 inches tall and 2 inches wide, the MB7621 is fairly inconspicuous. That’s perfect if you’re trying to keep electronic equipment from being the star of your home office.

If you don’t get Xfinity’s Gigabit plan, you can save a little money with the budget-priced NETGEAR CM500 modem. It supports wired internet speeds up to 680 Mbps.²

User reviews of the CM500 note that its installation was a breeze. So if you’re putting off getting your own modem because you’re not tech-savvy, give the CM500 a go.

Our only complaint about this modem (and all NETGEAR modems) is that it comes with only a one-year, limited hardware warranty.

The SURFboard SB8200 uses newer DOCSIS 3.1 technology to support download speeds up to 2,000 Mbps (or 2 Gbps).³ That’s perfect if you’re rocking Xfinity’s Gigabit internet plan—or if you’re running your home business on its 2,000 Mbps Gigabit Pro plan.

We’ve recommended ARRIS’s SURFboard routers before, so it’s no surprise to us that the SB8200 made it into our top-five lineup.

Xfinity’s xFi Gateway acts as both a modem and a router, so if you swap to your own equipment, you’ll need both. You can buy a modem and a router separately, or you can go for a combo like the NETGEAR Nighthawk C7000.

And, let’s face it. You could spend almost the same amount for just a modem. So the C7000 might save you more money in the long run.

The router also comes with excellent features and router settings like beamforming, which directs a Wi-Fi signal to a specific wireless device rather than any device in the area. (Think of it like lining up for a slam dunk versus blindly throwing 20 balls in every direction and hoping for a basket.) No need to put all your other wireless devices on airplane mode.

For those of us still rolling old school with a landline phone, you might need a modem that comes with a phone jack.

Not surprisingly, that’s hard to find these days. But the NETGEAR Nighthawk CM2050V packs in all the features into one eight-inch-high black box. You’ll get DOCSIS 3.1 technology that supports wired download speeds up to 2,500 Mbps, and you’ll get two phone jacks that are compatible with Xfinity Voice service.

Granted, all those features cost a pretty penny. So if cost-savings is what you’re after, you might try the cheaper ARRIS SBV3202—just be aware it supports speeds only up to 600 Mbps.

Our pick for the best Xfinity-compatible cable modem is the Motorola MB7621, thanks to its low price and support for wired speeds up to 1,000 Mbps. But if you don’t need gig speeds, the NETGEAR CM500 can save you a bit of cash with its budget-friendly price.

For anyone looking for the latest DOCSIS 3.1 technology and the ludicrous speeds it brings, the ARRIS SURFboard SB8200 and NETGEAR Nighthawk CM2050V are top-rated contenders. And those looking to replace the Xfinity xFi Gateway without having to buy a router as well should consider the NETGEAR Nighthawk C7000 modem and router combo.

1. Motorola MB7621: Best for most Xfinity internet plans, $89.99*, wired speeds up to 1,000 Mbps.¹
2. NETGEAR CM500: Best cheap cable modem, $73.00*, wired speeds up to 680 Mbps.²
3. ARRIS SURFboard SB8200: Best for gig internet plans, $144.49*, wired speeds up to 2,000 Mbps.³
4. NETGEAR Nighthawk C7000: Best modem and router combo device, $192.00*, wired speeds up to 960 Mbps.⁴
5. NETGEAR Nighthawk CM2050V: Best modem with phone jack for Xfinity Voice, $299.99*, wired speeds up to 2,500 Mbps.⁵

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