Short answer: look at your bill first. If it shows a monthly equipment charge you’d stop paying, your provider supports the device you want, and you’re happy to look after it yourself, buying usually pays off. If the equipment is already included at no extra charge, you rely on phone service over your cable line, or you’re only staying a short time, renting is often the better deal. There’s also a middle path: keep the provider’s box for the internet connection and add your own router for Wi-Fi.

Step 1: check what you’re actually paying for

Equipment pricing has changed. Xfinity, for example, now says its latest internet plans include the Xfinity Gateway at no extra cost. On a plan like that, buying your own modem doesn’t save anything on the bill, though you might still want your own router for better Wi-Fi.

On other plans and with other providers, a monthly equipment charge is common. Find it on your bill or plan details, then do the sum:

Check whether the charge covers a modem, a router, or a gateway that does both. Modem vs router vs gateway explains the difference if you’re not sure which box you have.

Step 2: check you can use your own

Providers decide which modems work on their network. Xfinity says you can use your own modem, router or gateway instead of renting, as long as the device works with Xfinity and supports your speed, and asks you to check compatibility on its device-lookup page before you buy. Other cable providers keep similar approved lists; check yours.

Older modems eventually drop off those lists. Xfinity says it won’t install, activate or recommend devices it has declared end-of-life. Buying a current DOCSIS 3.1 modem, like those on our best cable modems list, gives you the most time before that happens.

Fiber is usually simpler: you keep the provider’s fiber terminal and bring your own router, and providers such as gFiber document how.

What you take on, and what you give up

You take on the upkeep. Xfinity spells out that owners are responsible for keeping the device updated and secure, making sure it supports their speed, troubleshooting it, and managing Wi-Fi security.

You may lose provider features. Xfinity says its xFi app doesn’t work with third-party equipment, and that its WiFi Extenders, CyberSecure security service, hotspot access, pushed software updates and 24/7 support come with a rented gateway. Other providers bundle different features with their equipment; check what yours includes.

You may lose cable phone service. If your home phone runs over the cable line, a retail modem may not support it. NETGEAR, for example, says its CAX80 and CAX30S modem-router combos aren’t compatible with cable providers’ bundled voice service.

When buying makes sense

  • Your bill shows a monthly equipment charge, and you’ll keep the service long enough to break even.
  • You want better Wi-Fi than the provider’s box gives you, or features it lacks, such as a mesh system or more fast wired ports.
  • You don’t need cable phone service, and you don’t rely on the provider’s app or extenders.

When renting makes sense

  • The equipment is included in your plan at no extra cost.
  • You have phone service over the cable line.
  • You want the provider to handle updates, swaps and support, or you use its app, extenders or security service.
  • You’re moving soon or only staying a short time.

The middle path: keep their box, add your own router

You don’t have to choose all or nothing. Many people keep the provider’s gateway for the internet connection and put their own router (or mesh system) behind it. To avoid two routers fighting each other, the gateway goes into bridge mode, which turns off its routing but keeps the modem working. Xfinity notes the trade-off: in bridge mode you lose its network management and its WiFi Extenders. Double NAT explains what happens if you skip this step.

Next steps