Short answer: a LoRaWAN sensor’s battery life is set by four numbers: how often it reports, which spreading factor it uses, how much current it draws while asleep, and the usable capacity of its battery. Enter your device’s figures below and the calculator estimates the life in years, the airtime of each message and whether you stay inside the duty cycle and The Things Network’s fair use limit.
Numbers from a real device? Send them with your site details through our quote form and we will check the estimate against the sensor’s datasheet.
How does this LoRaWAN battery life calculator work?
It adds up the charge the device uses in one reporting cycle, spreads it over the reporting interval, adds the sleep current, and divides the usable battery capacity by that average. Self-discharge is taken off the capacity each year. Everything runs in your browser; nothing you enter is sent anywhere.
The airtime of each message uses Semtech’s LoRa time-on-air formula for a 125 kHz channel, with an 8-symbol preamble, explicit header, CRC on and a 4/5 coding rate, the defaults for EU868 LoRaWAN uplinks. The calculator adds 13 bytes of LoRaWAN overhead to your application payload: the MAC header, frame header, port and message integrity code. As a check, an 11-byte payload at SF7 comes out at 61.7 ms on air and at SF12 at 1,482.8 ms, which matches the standard LoRa airtime tables.
The two receive windows after each uplink are estimated as a short listen at the uplink’s spreading factor and a short listen at SF12, the EU868 default for the second window. If your device uses a different setting, untick the box and add the listening time into the measurement fields instead.
What drains a LoRaWAN battery fastest?
The spreading factor and the sleep current, usually in that order. With the example values on this page (4,000 mAh, 80% usable, 1% self-discharge, an 11-byte message every 10 minutes), the estimate is 15.8 years at SF7, 8.2 years at SF10 and 3.0 years at SF12. The only change is the spreading factor: an SF12 message spends 24 times longer on air than the same message at SF7.
Sleep current matters because the device spends almost all of its life asleep. Raising the whole-device sleep current from 10 to 50 microamps in the same example cuts the estimate from 15.8 years to 5.8 years, without sending a single extra message. That is why datasheet sleep figures deserve as much attention as transmit figures.
| Same sensor, one change | Airtime per message | Average current | Estimated life |
|---|---|---|---|
| SF7, every 10 minutes (example) | 61.7 ms | 18.5 µA | 15.8 years |
| SF10, every 10 minutes | 370.7 ms | 39.8 µA | 8.2 years |
| SF12, every 10 minutes | 1,482.8 ms | 116.4 µA | 3.0 years |
| SF12, every 60 minutes | 1,482.8 ms | 27.7 µA | 11.3 years |
| SF7, every minute | 61.7 ms | 94.9 µA | 3.7 years |
| SF7, sleep current 50 µA | 61.7 ms | 58.5 µA | 5.8 years |
Figures from this calculator with the example values above; your device’s datasheet currents will move them.
How do you make a LoRaWAN battery last longer?
- Put a gateway closer to the sensors. A stronger signal lets the network move a device from SF12 towards SF7 through adaptive data rate, which is the biggest single saving.
- Report less often. Many temperature and level readings change slowly; every 15 or 30 minutes is often enough.
- Send on change. Most industrial sensors can report immediately when a threshold is crossed and otherwise stay quiet.
- Keep the payload small. Every extra byte adds airtime, and at SF12 it adds a lot.
- Avoid confirmed uplinks. Asking for an acknowledgement on every message keeps the receiver on longer and can trigger retries.
- Mind the temperature. Cold freezers and hot plant rooms reduce usable capacity; lower the usable percentage for those sites.
What limits apply to LoRaWAN airtime in the UK?
In the 868.0 to 868.6 MHz sub-band used by the three default EU868 channels, a device may transmit for 1% of the time, which is 36 seconds in any hour. The calculator shows your airtime per hour against that figure. Other EU868 sub-bands carry different limits, so treat the 36 seconds as a guide for the default channels rather than a total for every frequency.
If your devices use The Things Network’s public community network, its fair use policy also limits each device to 30 seconds of uplink airtime per day. On a private network server that limit does not apply, but the duty cycle still does.
How accurate is the estimate?
It is only as accurate as the currents you enter. The example values are round numbers for a typical battery sensor, not the figures for any particular product, so replace them with the numbers from your device’s datasheet. Real batteries also lose capacity in the cold and under repeated current pulses, which is what the usable-capacity field is for.
Use the result to compare options, such as SF7 against SF10 or a 10-minute against a 30-minute interval, rather than as a guarantee. For a site survey or a check against a specific sensor, browse our LoRaWAN sensors, see how to choose a LoRaWAN gateway, or read LoRaWAN vs NB-IoT for how the two compare on cost of ownership.
Related guides: how long LoRaWAN sensor batteries last, LoRaWAN gateway calculator.
Frequently asked questions
How long does a LoRaWAN sensor battery last?
Typically several years, and often more than ten for a sensor reporting every 10 to 30 minutes at a low spreading factor. The same sensor at SF12 can last a fraction of that. Enter your device’s reporting interval, spreading factor and currents in the calculator above for an estimate.
Does the spreading factor affect battery life?
Yes, more than anything else. Each step up in spreading factor roughly doubles the time on air. With the example values on this page, the same 11-byte message every 10 minutes gives about 15.8 years at SF7 and about 3.0 years at SF12.
What battery do LoRaWAN sensors use?
Most long-life LoRaWAN sensors use lithium thionyl chloride cells because they hold a lot of charge, lose little to self-discharge and work in the cold. Some use standard lithium or alkaline batteries. Check your device’s datasheet for the exact cell and capacity.
Why does my calculated battery life differ from the datasheet?
Manufacturers quote battery life for specific conditions, such as a set reporting interval, spreading factor and temperature. If your site uses a different interval, sits further from the gateway or runs colder, the real life will differ. Enter your actual conditions to compare.
How much airtime can a LoRaWAN device use?
In the default EU868 sub-band, 1% of the time, or 36 seconds per hour. On The Things Network’s public network, the fair use policy also limits each device to 30 seconds of uplink airtime per day.