Short answerA SIM-only data plan gives you a SIM and a monthly allowance with no device attached. For a router, choose a data-only plan that explicitly allows router use, size the allowance from real usage, and prefer a 30-day rolling term until you know the network works at the site.
SIM-only is how most routers get connected. You buy the router once, then pay for the data separately, which means you can change network without changing hardware.
Estimate the data you will use
Guessing is how people end up with a SIM that runs out on the 12th of the month. Some rough figures help:
- Telemetry, meters and alarms: usually megabytes, not gigabytes, a month.
- Card payment terminals and tills: small amounts of data, but they must never drop.
- A small office using cloud apps: often tens to a few hundred gigabytes a month.
- CCTV viewed remotely: depends on how often people watch and at what quality. Cameras that upload continuously to the cloud use far more.
If the router is already running, its data usage page is the best guide. Most business routers, including Teltonika’s, show usage per SIM and can warn or switch SIM at a limit.
The small print that matters in a router
Router and tethering use
Some plans, especially phone plans and cheap “unlimited” deals, exclude routers. Check the terms say mobile broadband, router or business data.
Fair use on unlimited plans
Unlimited usually means unlimited within a fair use policy. Heavy users can be slowed at busy times. Read the policy before you rely on it for a whole office.
What happens at the limit
Some plans stop the data, some slow it, some charge for extra. For an unattended site, a plan that slows is safer than one that stops.
Contract length
Start on a 30-day rolling plan. Once you know the network performs at the site, a longer contract may save money.
IP address
Standard plans give a private address behind carrier-grade NAT. If you need to connect in, see fixed IP SIMs.
Consumer, business and IoT plans
| Consumer data | Business data | IoT / M2M | |
|---|---|---|---|
| Typical buyer | Home user | Company with a few sites | Fleets of devices |
| Allowance | Per SIM | Per SIM or shared | Usually pooled |
| Fixed IP option | Rare | Common via resellers | Common |
| Multi-network | No | Sometimes | Often |
| Management portal | Basic app | Account portal | Per-SIM control and alerts |
For more on the IoT side, read IoT and multi-network SIMs.
Frequently asked questions
Is a SIM-only data plan cheaper than a router bundle?
Over a year or two it usually is, and you keep the freedom to change network. Bundles make sense when you want one bill and one supplier.
Can I move a data SIM between routers?
Usually yes. Some business and IoT SIMs are locked to a device’s IMEI for security, so check before moving one.
Do data SIMs work abroad?
Some do, at extra cost. For equipment that regularly crosses borders, a roaming IoT SIM is normally better value.
Not sure how much data a site will use? Ask us and we will help you size it.
NANick Appleby
Nick Appleby has worked in UK telecoms since 1998, starting at BT, and has spent most of that time on cellular routers, data SIMs and the antennas that connect them for business and industrial sites. He writes 4G SIM to explain how the networks and the kit actually behave, in plain English.