Smart meter frequencies and protocols

Most North American electric, gas, and water meters broadcast in the 902 to 928 MHz ISM band. The common message formats are Itron's ERT family — SCM, SCM+, and IDM — plus Neptune's R900 for water. Each message carries a meter ID and a cumulative consumption count, sent unencrypted every few seconds to minutes.

What frequency do smart meters transmit on?

In the United States and Canada, meter endpoints live in the 902 to 928 MHz ISM band, with most consumption traffic clustered around the middle of it. Practical receivers usually park near 912 MHz because that captures the bulk of the activity in one gulp.

The band is unlicensed and shared, so meters coexist there with cordless phones, industrial telemetry, and a long tail of other low-power devices. That is also why a receiver in a dense neighbourhood hears dozens of endpoints: everyone's meter is transmitting into the same slice of spectrum, and nothing addresses the message to a particular listener.

Europe and much of the rest of the world use different allocations, commonly around 868 MHz, and different meter standards entirely. The guidance here is specific to North American deployments.

What is an ERT?

ERT stands for Encoder Receiver Transmitter — Itron's family of automatic meter reading endpoints. An ERT is the radio module that sits on or inside the meter, reads the register, and broadcasts the value so that a drive-by truck or a fixed collector can log it without anyone walking up to the meter.

ERT modules are attached to all three utility types. Electric meters typically have the radio integrated into the meter body; gas and water meters more often have a separate module strapped to the register, because those meters have no power source of their own and the module runs off a long-life battery.

SCM, SCM+, and IDM

These are the message formats an ERT sends, not different radios. The differences matter mostly for whichever software is doing the decoding.

• SCM (Standard Consumption Message) is the classic and most widely seen format. It carries the endpoint ID, a cumulative consumption count, a commodity type, and tamper flags.
• SCM+ is a later framing that carries broadly the same information with a different packet structure. Newer endpoints tend to send it.
• IDM (Interval Data Message) is the interesting one: rather than a single running total, it carries a series of recent interval buckets alongside the total, so a single received packet describes the shape of consumption over the preceding period, not just one instant.

R900 and water meters

R900 is Neptune's endpoint protocol, used widely on water meters and also in the same 900 MHz band. Like the ERT formats it carries an endpoint ID and a cumulative volume, and like them it is sent in the clear.

Water meters are the most battery-conscious of the three, so their endpoints are often the least chatty — a longer gap between transmissions is normal and not a sign that something is misconfigured.

Protocol reference

How often does a meter transmit?

Typically every 30 seconds to a few minutes, depending on the endpoint type and how the utility configured it. Electric endpoints, which have mains power to draw on, are generally the most frequent; battery-powered gas and water endpoints transmit less often to stretch their service life.

Nothing you do speeds this up. These are one-way broadcasts on the endpoint's own schedule — a receiver cannot poll a meter, and Utilify does not transmit anything at all.

Why some meters cannot be read

Not every meter is receivable, and it is worth knowing that before spending money on hardware. Some utilities have moved to mesh AMI networks with encrypted payloads, where the traffic is present but unreadable. Some endpoints use proprietary formats no open decoder handles. And older mechanical meters with no radio at all broadcast nothing.

Checking the meter face for an ERT marking, or simply asking your utility what endpoint they installed, saves a lot of guesswork.

What the readings actually mean

The consumption value in these messages is a cumulative counter, like an odometer, not a rate. Usage across an interval is the difference between two readings, and the unit is scaled per endpoint — kilowatt-hours for electric, hundreds of cubic feet or cubic metres for gas, gallons or cubic feet for water. Comparing a captured day against a known figure on your bill is the reliable way to pin down the multiplier for your meter.

Values received over the air are informational. Treat your official utility bill as the authoritative record.

Receiving your own meter

Utilify decodes SCM and R900 packets from most North American electric and gas smart meters on 912 MHz, stores them in a local SQLite database on your device, and charts them against historical temperature. It only receives, and it is licensed for monitoring meters you own or have explicit authorization to monitor. For the hands-on setup, see the step-by-step RTL-SDR guide.