What “Low Power” Actually Means: A Reality Check on Battery Life Expectations in the World of LTE-M and NB-IoT

TL;DR

• The “10-year battery life” figure boasted on LTE-M and NB-IoT devices is a best-case design target built on idealized assumptions, not a promise your deployment will keep.
• Real battery life depends on reporting frequency, coverage, network behavior, connection overhead, firmware, and the battery itself, most of which a datasheet never mentions.
• Treat battery life as a system-level business decision, measure it in the field, and put battery replacement costs into your TCO model from day one.

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The Number on the Datasheet

It usually starts with a single line on a module datasheet: “up to 10 years of battery life.” That line finds its way into a business case. Then a pricing model. Then, sometimes, a customer contract.

Eighteen months after launch, the first devices start going quiet.

For a battery-powered IoT fleet, the battery is the service life of the device. When it runs out, someone has to go to the device. Industry estimates for a single field visit to service a device, such as swapping a physical SIM or battery, commonly range from roughly $50 to $500 per device depending on location and access.

Remote SIM provisioning (an eUICC capability) has made many SIM-related truck rolls avoidable. Nobody has invented an over-the-air battery.

LTE-M and NB-IoT are some of the most important technologies in IoT because they make multi-year battery life possible. That being said, it is important to note that “low power” is a capability, not a guarantee. Whether a deployment actually gets there depends on decisions made in the business case, the firmware, and the network – and most of those decisions have almost nothing to do with the battery.

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Where “10 years” Actually Comes From

The 10-year figure isn’t a marketing invention. It traces back to design targets set by 3GPP when it studied what low-power cellular IoT should be able to do. In Technical Report 45.820, one of the stated objectives was a device that could reach up to ten years of battery life on a 5 Wh battery, even in locations with poor coverage.

The words “up to” in that objective carry a lot of weight. Ten years was a ceiling to design toward, not a floor. The sample calculations 3GPP later ran to evaluate candidate designs assumed small messages sent infrequently, and the results swung widely depending on how often a device reported and how difficult its coverage was.

In 3GPP’s own calculations, results ranged from roughly 6 years in the hardest coverage conditions with frequent reporting to more than 20 years in the most favorable scenarios.

Even well-designed real-world devices tend to land short of the headline. In a past post on avoiding paying for connectivity you don’t use, we noted that an LTE-M device transmitting once per day could last approximately 4.7 years on two AA batteries. That’s a strong result, but obviously falls well short of the ten year lifecycle marketers love to band about.

The fairest way to read the headline number: 10 years was a design target for an idealized device, not a forecast for yours.

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What Actually Drains the Battery

Battery life is a system property, not a component spec. No single part, including the module or the SIM, determines it.

Here are the variables that do. Most leaders will never tune them directly, but knowing they exist changes the questions you ask.

1. How Often You Talk, and How Much You Say
Reporting interval and payload size are the single biggest lever on IoT battery life. A device that reports hourly will not last as long as one that reports daily, no matter how efficient the radio.

This is a business decision disguised as a technical one. The real question is, “What decisions does this data drive, and how fresh does it need to be to drive them?”

2. Where the Device Lives
A device on a well-covered street corner and the same device in a basement meter pit are two very different power consumers.

In weak coverage, devices transmit at higher power and, on LTE-M and NB-IoT, often repeat their transmissions many times to get a message through. The same hardware can burn through its battery several times faster in poor coverage than in good coverage.

3. What the Network Actually Grants
The two main battery-saving features in LTE-M and NB-IoT are Power Saving Mode (PSM) and extended Discontinuous Reception (eDRX). In plain terms, both let a device sleep for long stretches instead of constantly listening to the network. (Learn more about this process here.)

Here’s the part that rarely makes it into a business case: the device requests these sleep settings, and the network grants them. The network can accept them, shorten them, or ignore them. Support varies by carrier, by country, and by roaming partner.

A battery estimate built on the settings a device asked for, rather than the ones it received, can be fiction in the field.

4. Connection Overhead Nobody Budgeted For
Waking up to send 50 bytes of sensor data can mean exchanging far more than 50 bytes. Attaching to the network, looking up addresses, and especially setting up encrypted TLS sessions all take airtime and energy.

For small, infrequent messages, that overhead can cost more energy than the data itself.

5. Firmware Behavior When Things Go Wrong
Batteries rarely die on a good day. They die during retry loops, repeated failed attempts to join the network, and poorly timed firmware updates.

A device that handles a coverage gap badly can drain itself trying to reconnect, then go silent right when you need it.

6. The Rest of the Device
The radio is not the only thing drawing power. GPS, sensors, and the device’s own processor can all outdraw it. This is to say nothing of the potential issues that can arise from antenna performance issues or hardware inefficiencies.

“Low power connectivity” does not automatically make a low power device.

7. The Battery Itself
A battery’s rated capacity and its usable capacity are not the same thing. Temperature extremes, self-discharge over years on a shelf or in the field, and how certain battery chemistries respond to the short, high-current bursts a radio demands all shave real-world life.

Exact losses vary widely by chemistry and conditions, which is exactly why they belong in the planning conversation rather than as a footnote.

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LTE-M vs. NB-IoT: Which is Better for Battery Life?

A common assumption is that NB-IoT is always the lower-power choice. The reality is more nuanced.

NB-IoT generally suits stationary devices that send very small, infrequent messages. It’s also known for strong deep-indoor coverage.

LTE-M moves data faster, which means less time with the radio switched on for larger payloads or firmware updates. It also supports devices that move between cell towers, and in many regions it has broader roaming availability. For some use cases, those traits let LTE-M come out ahead on battery.

If your devices…	Lean toward
Are stationary and send tiny, infrequent messages	NB-IoT
Sit deep indoors or underground	NB-IoT (coverage permitting)
Move, or need handover between cells	LTE-M
Send larger payloads or need regular firmware updates	LTE-M
Deploy across many countries	LTE-M (check local availability for both)

The right answer depends on your payload, mobility, coverage, and which networks are actually available where your devices ship. Regional support for both technologies continues to change, so check current availability for your target markets before committing.

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A Reality Check: Questions to Ask Before You Trust a Battery Number

This is where leaders can make the biggest difference. You don’t need to read a power profile to ask good questions of your engineering team or device vendor.

• What assumptions sit behind this number?
  Reporting interval, payload size, signal strength, temperature, and battery chemistry.
• Was it measured or calculated?
  And if measured, was it on a live network using the power-saving settings the network actually granted, or on a bench?
• Which networks and countries does it hold for?
  This matters most for multi-country and roaming deployments.
• What happens in the worst case?
  Poor coverage, a network outage, a failed firmware update.
• Is battery replacement in the TCO model?
  If not, the business case is optimistic by design. We explore this pattern of hidden lifecycle costs in more depth in our eBook, Why Cheap Hardware Is the Most Expensive Mistake.
• How will we know a battery is failing before the device goes silent?
  Battery voltage and connection health should be reported as data, not discovered on a site visit.

That last point deserves emphasis. A device with a dead battery and a healthy device with nothing to report both produce the same signal: silence. We dig into that problem a bit more thoroughly here.

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How Soracom Helps Close the Gap

Soracom can’t change the laws of physics, but we can help with several of the variables above.

Tuning sleep settings from the network side.
Soracom lets customers configure requested eDRX and PSM timers at the SIM group level, so they’re sent to the network when devices attach, without modifying device firmware. As noted above, the local network still has the final say. For teams working through timer values, our PSM Calculator helps generate and decode them.

Cutting connection overhead with Soracom Beam.
Soracom Beam is a protocol conversion and TLS offloading service. It converts lightweight device traffic (HTTP, TCP, UDP, or MQTT) into secure HTTPS or MQTTS before forwarding it to the cloud. Because devices avoid establishing TLS sessions themselves, they can significantly reduce transmission time and improve battery life. Soracom Beam also injects credentials inside the Soracom platform, so API keys and certificates don’t need to live on the device, and settings can be updated at the SIM group level for an entire fleet at once.

Seeing silence for what it is.
Connectivity and session data from the Soracom platform, combined with battery voltage reported as ordinary telemetry, help teams tell the difference between “quiet because healthy” and “quiet because the battery is gone.”

Better coverage options.
Access to multiple networks in many regions can help devices find better signal, which directly affects how hard the radio has to work. How network selection behaves depends on the device, plan, and region.

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Plan For the Battery Life You’ll Actually Get

LTE-M and NB-IoT deliver real, meaningful power savings. The problem isn’t the technology. It’s treating a best-case design target as a planning assumption.

The organizations that achieve multi-year battery life treat it as a shared design goal across business, engineering, and connectivity. They decide how often data really needs to move, they test on the networks where devices will actually live, and they measure battery health in the field instead of waiting for devices to go dark.

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If a battery-powered deployment is on your roadmap, talk to Soracom’s IoT experts about testing real-world power behavior on your target networks, or start with our PSM Calculator.

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FAQ

• Is 10-year battery life realistic for NB-IoT and LTE-M devices? It can be, but only under favorable conditions: small, infrequent messages, good coverage, network support for power-saving features, and a well-behaved device. Many real deployments land well short of it.
• Where does the 10-year battery life claim come from? It comes from a 3GPP objective of up to ten years of battery life on a 5 Wh battery, even in poor coverage. 3GPP’s later sample calculations showed results varying widely with reporting frequency and coverage conditions.
• Which is better for battery life, LTE-M or NB-IoT? Neither wins universally. NB-IoT often suits stationary devices sending tiny messages, while LTE-M’s faster data rates and mobility support can make it more efficient for larger payloads, moving devices, or frequent firmware updates.
• What are PSM and eDRX? They are power-saving features that let LTE-M and NB-IoT devices sleep for long periods instead of constantly listening to the network. The device requests the settings, but the network decides what to grant.
• Why is my IoT device battery dying faster than expected? Common causes include more frequent reporting than planned, poor coverage, power-saving settings the network didn’t grant, connection and encryption overhead, firmware retry loops, power-hungry sensors, and temperature effects on the battery.