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SimFalcon guide

Solar and battery monitoring over a SIM: a UK checklist for dropouts

UK 3G has largely gone and 2G now has dates attached, so the radio inside a monitoring dongle matters more than it did. This guide covers the network timetable, what MCS and Ofgem do and do not say about monitoring, and the checks to run before you replace a logger.

Where the network timetable stands

These are the operators' own statements as read on 3 October 2026. Dates can change, so confirm with your supplier.

Network3G2G
EESwitched off in January and February 2024 [8]Closing begins May 2029 [8]
VodafoneSwitched off in 2024 [9]To be switched off in spring 2030 [10]
ThreeSwitched off at the end of 2025 [10]Never had a 2G network [10]
O2 (Virgin Media O2)Most switched off; O2's page said some areas might keep a signal in early 2026 [11]Switching off from 2029 [11]

All the providers have told the UK Government they do not plan to offer 2G and 3G services beyond 2033 [12].

What that means for a monitoring dongle

A dongle that supports 4G is less exposed to these dates. The risk sits in older modems.

EE tells businesses with 2G or 3G-only tills, security systems or telemetry devices to plan an upgrade to 4G or 5G [8]. Vodafone says the majority of IoT and M2M devices are already compatible with other technologies such as 4G, 5G, NB-IoT or LTE-M, and asks businesses relying on 2G to contact their service supplier [10]. None of the operator pages used here names solar or battery monitoring, so check the radio in each model rather than wait for a notice.

Installation and plan causes that look like network faults

Why a dropout matters in the UK

For MCS-certified installations, standard MIS 3002 (issue 5.0) says a means of notifying the customer within 48 hours of the system ceasing to operate, or beginning to operate abnormally, should be provided. The clause's note says a MID-approved meter installed under clause 5.7.2 could satisfy that [14]. Where monitoring is the method, a dead link removes the warning.

The next clauses say that where an installation includes internet-connected devices, their network access credentials (usernames and passwords) must be updated in consultation with the customer. In commercial and industrial premises that need local area network, home area network or internet access, permission must be obtained from those responsible for the client organisation's information technology and information security policies [14]. A logger with its own SIM may not touch the client's network at all, so it is worth asking whether their IT policy still wants to be told.

Smart Export Guarantee payments are a separate matter. Ofgem says they are calculated using export meter readings [15]. How your export is metered and read depends on your installation, so if you are unsure whether a monitoring fault could affect payments, ask your SEG licensee.

SIM format, APN, PIN and data

SIM sizes vary by product. Victron's GX LTE 4G and Huawei's SmartDongle-4G take Mini-SIMs [1][6]. SolarEdge's 2019 plug-in guide specifies a Nano SIM and says non-SolarEdge SIMs need a minimum inverter firmware version [7]. Victron says some networks need the APN set manually, and that an unset APN can leave a registered modem offline [1]. Victron's status list reports “PIN required” for a PIN-locked SIM, which is worth ruling out first [1].

Data needs are small but real. For its SDongleA-03, Huawei lists a monthly requirement of 10 MB plus 4 MB for each inverter, with extra allowances for optimisers and power sensors [2]. SimFalcon's UK page adds that firmware updates and reporting frequency can change usage materially [16]. Find the figure for your own model.

What a multi-network SIM changes

SimFalcon's UK solar page says selected multi-network connectivity can reduce dependence on one local network where an inverter sits in a weak-signal or rural spot. It lists six checks before ordering: the exact device model, whether the SIM is removable or embedded, whether the APN can be set, whether the module supports the mobile technologies on site, expected data use, and coverage at the actual inverter or enclosure location, not just inside the house or office [16].

Before you replace the logger

  1. Confirm with the inverter display or lights that the system is generating. If only monitoring is down, it is a connectivity job.
  2. Note the exact logger model and region code, and what its manual says about 2G, 3G and 4G.
  3. Check for an ended plan or an empty pay-as-you-go SIM, then the SIM seating, size and PIN.
  4. Use the device's status page or light code to place the fault: SIM, signal, settings or server [2][7].
  5. Test signal at the antenna position and try moving the antenna.
  6. Check whether Wi-Fi or a cable is taking priority over the cellular link.
  7. Record the findings in the handover file, then ask the manufacturer or installer about firmware or a 4G replacement.

Our SIM not connecting, APN setup, weak or no network and replacing the SIM guides cover the basics. The solar monitoring SIM page sets out the six checks before ordering and what device details to send, and pricing covers plans and billing. We sell managed SIMs, so we have kept our own claims to what our pages say and cited everything else to its source: a manufacturer, operator or regulator, or, where the source list says so, a retailer's page hosting a manufacturer document.

Sources

Frequently asked questions

Has 3G been switched off in the UK?

The operators' own pages say EE and Vodafone switched off 3G, in 2024, and Three at the end of 2025. O2's page said most of its 3G had gone, with some areas possibly keeping a signal in early 2026.

When does UK 2G close?

EE says from May 2029, O2 from 2029 and Vodafone in spring 2030. All the providers have told the Government they do not plan to offer 2G and 3G beyond 2033.

Does an offline dongle affect Smart Export Guarantee payments?

Ofgem says SEG payments are calculated by using export meter readings. Whether a monitoring fault could affect your payments depends on how your export is metered and read, so ask your SEG licensee if you are unsure.

Can a new SIM add 4G to a 2G and 3G-only modem?

No. A SIM cannot add a radio the device lacks, so a 2G and 3G-only modem stays that way. Victron's GX GSM is one such modem, and Victron names a 4G model as its replacement.

What should I check before replacing a logger?

Check the inverter is generating, the model's supported radios, any ended or empty plan, the SIM seating, size and PIN, signal at the antenna, and whether Wi-Fi or a cable is taking priority.

Questions about connectivity for your equipment? Talk to SimFalcon or ask Engineer Support.

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