IoT SIM data allowances: how much your devices really use
Picking a data allowance is arithmetic once you know what a device sends and how often. Here are published figures for common devices, worked examples, and how to map the result to a monthly plan for UK sites.
The method
Data use is a size multiplied by how often it happens. For messages, that is message size times the number of messages. For video, it is bitrate times time. Everything else is detail.
- Messages: bytes per message × messages a day × 30.
- Video: kilobits per second × seconds ÷ 8 = kilobytes.
We use decimal units (1 MB = 1,000,000 bytes). The sums in this guide are our own arithmetic from the sourced figures, not measurements of any product.
Small messages carry overhead. Every IPv4 packet has at least a 20-byte header [3], and TCP adds at least 20 bytes more [4]. On a 66-byte message that is 40 bytes before the server’s reply, so sending several readings per packet saves a lot.
GPS trackers
Teltonika’s Codec 8 protocol shows how small a position is. Each record has an 8-byte timestamp, a 1-byte priority, a 15-byte GPS element (position, altitude, angle, satellites, speed) and a variable block of input/output data. Teltonika gives 45 bytes as the smallest record with all I/O switched off, and its first worked example is a 66-byte packet carrying one record. Over TCP the server replies with the number of records received, and the tracker resends if the count is wrong [1]. Trackers can also hold records and send them in batches [2].
Worked example. A van drives three hours a day and logs a position every 30 seconds: 360 records a day. Sent one per packet, each send is about 106 bytes out (66 plus 40 bytes of headers) and 44 bytes back (a 4-byte reply plus headers): roughly 54 kB a day, or 1.6 MB in 30 days. That is a floor; it leaves out connection set-up, keep-alives and extra I/O data. Logging every few seconds, many I/O values or firmware updates multiply it. The 10MB plan suits a lightly configured tracker; the 50MB plan gives room for frequent logging.
Alarm panels and communicators
Alarm communicators report by voice call or over data [20], and data use varies widely. Ajax’s FAQ for its Hub, last updated in 2019, says it uses up to 10 MB a day in normal mode without alarms, depending on settings and the number of devices [5]. That is up to about 300 MB in 30 days, far more than a tracker. Ask the panel maker for its own figure.
SimFalcon alarm plans are voice-and-data plans. SimFalcon SIMs do not send or receive SMS, so panels that only alert by text are not suitable [20]. See alarm SIMs.
GSM gate openers and intercoms
Most of the work here is voice, not data. A call-to-open unit such as the RTU5034 checks the caller ID against up to 200 authorised numbers, rejects the call and switches its output on the first ring, so the caller is not charged; unknown callers are ignored. It can be set up by app or by SMS command [6]. Opening by call uses no mobile data, so data only matters if the unit also uses an app or cloud service; ask the maker for that figure.
Two things matter more than the allowance. SimFalcon SIMs do not send or receive SMS, so a unit that can only be configured or controlled by text needs another way in, such as its app. And SimFalcon gate and intercom plans are voice-and-data plans that include a local UK geographic number for callers to ring [19]. See gate access SIMs and our guide to local dial-to-open numbers.
Card payment terminals
Adyen’s documentation, as one example, says its terminals connect out over HTTPS using TLS 1.2, need a working DNS server, and can carry on over cellular through a built-in modem or a cellular router [7]. We did not find a per-transaction data figure published by a payment provider, so ask yours for a monthly estimate, including software updates, before choosing a plan.
Telemetry: solar, EV chargers and building systems
Telemetry is regular readings, so it is predictable once you know the interval. A 2019 SolarEdge datasheet for its cellular plug-in, an older 3G-era kit, lists monthly data per device in two modes [8]. Use it for the method rather than as figures for a new installation.
| Device | High bandwidth: sampled every 5 minutes, sent continuously | Low bandwidth: sampled every 15 minutes, sent every 4 hours |
|---|---|---|
| Inverter | 7.8 MB | 2.6 MB |
| Power optimiser | 0.15 MB | 0.05 MB |
| Export or consumption meter | 3 MB | 0.55 MB |
| Battery | 3 MB | 0.7 MB |
A home system with one inverter, 20 optimisers, a consumption meter and a battery comes to 16.8 MB a month in high-bandwidth mode, which suits the 50MB plan. Low-bandwidth mode would be under 5 MB, but the same datasheet says a third-party SIM used in that mode must support SMS [8], which SimFalcon SIMs do not [19].
EV chargers send more. Charger maker Etrel says chargers normally exchange 30 to 100 MB a month, more if they send meter readings very often, are busy, or are often asked for diagnostic logs, which can reach a couple of MB. Firmware files run from 7 MB to 85 MB depending on the vendor, though updates normally happen less than once a month [9]. A charger at the top of that range taking one large update uses about 185 MB, so the 500MB plan is the safer choice; the 100MB plan suits a quiet charger with rare updates. Our EV charger guide covers the connection itself.
Building and boiler monitoring depends on how many points are polled and how often, so measure one site before choosing for many. See our BMS and boiler monitoring guide.
4G routers
A router adds its own traffic before any device behind it sends a byte. Teltonika said in a 2020 webinar that its RMS remote management uses about 3.54 MB down and 8.44 MB up per router per month at default settings [10]: about 12 MB, more than the 10MB plan on its own. A single firmware file is about as much again: the RUT241 stable firmware released on 12 October 2026 is 12 MB [11]. Then add every device behind the router; a router serving a CCTV recorder needs a video-sized plan.
Teltonika routers can set a data limit that switches mobile data off when reached, resetting daily, weekly or monthly [12]. The same screen offers an SMS warning [12], which will not work on a SimFalcon SIM [19].
4G CCTV: where the data goes
Video outweighs everything else in this guide. Reolink publishes default bitrates and recommended monthly data for its 4G cameras [13]:
- Go and Go PT: 1.5 Mbps main stream, 160 kbps sub-stream; 1 GB gives about 1.5 hours of main-stream viewing or 14 hours of sub-stream; 1 GB a month recommended for normal use.
- Several other models: 2 Mbps main, 672 kbps sub; about 1 hour or 3.5 hours per GB; 2 GB a month recommended.
- Events: images a few hundred KB each, videos up to 2 MB each. Recording to the SD card uses no data.
Worked example. A camera uploading 25 motion clips a day at up to 2 MB each uses up to 1.5 GB in 30 days. Ten minutes of sub-stream viewing a day at 672 kbps adds about 1.5 GB. Together that is about 3 GB, so the 5GB plan fits. Continuous upload is a different scale: a steady 1 Mbit/s stream is about 324 GB in 30 days. For towers and multi-camera sites, see our CCTV tower guide.
Why leave headroom
- Firmware. One update can outweigh months of normal traffic: 12 MB for a Teltonika router file [11], 7 to 85 MB for a charger [9].
- Diagnostics and resends. Log uploads [9] and resent tracker records [1] all count.
- Video settings. Higher camera settings use more data [13], and viewing habits change.
- Overhead. Headers and replies can be a large share of small messages [3][4].
Our rule of thumb: choose a plan at least half as big again as your estimate, so a third of it stays spare, then check real use after the first month on the device’s or router’s own counter.
Matching the estimate to a plan
| Plan | Estimate it fits, keeping a third spare | Examples from this guide |
|---|---|---|
| 10MB | Up to about 6.5 MB | Tracker logging every 30 seconds while moving |
| 50MB | Up to about 33 MB | Home solar system on high-bandwidth monitoring; a router’s own management traffic |
| 100MB | Up to about 66 MB | EV charger at the low end of Etrel’s range |
| 500MB | Up to about 330 MB | EV charger at the top of the range, with a firmware update |
| 1GB | Up to about 660 MB | Camera sending ten 2 MB clips a day, with no live viewing |
| 5GB | Up to about 3.3 GB | Camera with 25 clips and ten minutes of sub-stream viewing a day |
| 10GB | Up to about 6.6 GB | Camera with ten minutes of 2 Mbps main-stream viewing a day (about 4.5 GB) plus clips |
Check the radio before the allowance
Mobile UK says UK providers will not offer 2G or 3G beyond 2033, that devices limited to 2G or 3G will need replacing with 4G or 5G-capable models, and that virtual networks follow their parent network’s schedule [18]. Confirm a device has a 4G radio before sizing its plan; see our 2G and 3G switch-off guide.
Choosing a SimFalcon plan
SimFalcon sells managed multi-network IoT SIMs, with data plans from 10MB to 10GB a month. Plans are 12 months of service paid upfront, then renew yearly by Direct Debit, and gate, intercom and alarm devices use voice-and-data plans instead [19][20]. Not sure? Find your SIM or browse all SIM cards.
Sources
- [1] Teltonika, Codec, checked 22 October 2026.
- [2] Teltonika, FMB920 data acquisition settings, checked 22 October 2026.
- [3] IETF, RFC 791, checked 22 October 2026.
- [4] IETF, RFC 9293, checked 22 October 2026.
- [5] Ajax Systems, How much traffic does the Hub use via GPRS?, checked 22 October 2026.
- [6] BLIIoT, RTU5034 gate opener, checked 22 October 2026.
- [7] Adyen, Point-of-sale network configuration, checked 22 October 2026.
- [8] SolarEdge, Cellular plug-in datasheet, checked 22 October 2026.
- [9] Etrel, SIM: mobile bandwidth usage, checked 22 October 2026.
- [10] Teltonika, RMS webinar Q&A, 26 March 2020, checked 22 October 2026.
- [11] Teltonika, RUT241 firmware downloads, checked 22 October 2026.
- [12] Teltonika, RUT956 mobile settings, checked 22 October 2026.
- [13] Reolink, Data use of Reolink 4G cameras, checked 22 October 2026.
- [18] Mobile UK, 2G and 3G switch-off, checked 22 October 2026.
- [19] SimFalcon, Gate access SIM (UK), checked 22 October 2026.
- [20] SimFalcon, Alarm standard SIM (UK), checked 22 October 2026.
Frequently asked questions
How much data does a GPS tracker use?
Not much if it is set up sensibly. On our arithmetic from Teltonika's Codec 8 figures, a tracker logging every 30 seconds for three hours a day sends roughly 1.6 MB a month before connection overheads. Frequent logging, extra I/O data and firmware updates add more.
Is a 10MB plan enough for a 4G router?
Usually not on its own. Teltonika said in 2020 that its RMS remote management uses about 12 MB a month per router at default settings, and a single RUT241 firmware file is 12 MB. Then add whatever is connected to the router.
How much data does a 4G CCTV camera use?
It depends on bitrate and viewing. Reolink says 1 GB gives about one hour of main-stream viewing on several of its 4G cameras, and recommends 1 to 2 GB a month for normal use on those models. A continuous 1 Mbit/s upload would be about 324 GB a month.
Can I use a data-only SIM in a gate opener or alarm?
Not if it needs voice. Call-to-open gate units and alarms that report by voice call need a voice-and-data plan, which is what SimFalcon's gate, intercom and alarm plans are. SimFalcon SIMs do not send or receive SMS, so SMS-only devices are not suitable.
Why leave headroom on an IoT data plan?
Because firmware updates, diagnostic uploads, resends and changes in viewing habits are hard to predict. Etrel says EV charger firmware files run from 7 MB to 85 MB, which on its own can exceed a small plan.
Questions about connectivity for your equipment? Talk to SimFalcon or ask Engineer Support.