The best-reviewed monitor in this guide (about 4.7 stars from 2,461 ratings), the Pro 3EM measures three phases with 120 A clamps and tracks energy in both directions, so it’s the standard choice for three-phase homes and for anyone measuring solar export. It also works perfectly on single-phase and split-phase systems by using the channels for different circuits. Like the Pro EM, it connects over Ethernet or Wi-Fi and integrates locally with Home Assistant’s Energy dashboard. Only 3 were in stock when we checked.

To meter one specific appliance or circuit, such as a freezer, a home office or a heat pump, the tiny PM Mini Gen3 (about 4.6 stars from 1,408 ratings) fits behind a socket or inside a junction box and measures up to 16 A. It’s a pure meter with no relay. It runs on Shelly’s Gen3 platform, which uses an ESP32-C3-class module, and it works locally with Home Assistant. The ESPHome device database lists it too, though Gen3 firmware is signed, so ESPHome requires serial flashing.

The EM Mini Gen4 (about 4.5 stars from 147 ratings) is Shelly’s newest compact meter, built on the Gen4 ESP32-C6 platform. Its 802.15.4 radio means it can join a Zigbee network or a Matter ecosystem as well as Wi-Fi, so it fits homes built around Apple Home, Google Home or a Zigbee coordinator. The ESPHome community is still working on full Gen4 energy-meter support, so treat this as a stock-firmware device for now.

The PZEM-004T is the classic DIY AC meter: a calibrated metering board that measures voltage, current, power, energy, frequency and power factor and sends the results to an ESP32 over an isolated TTL UART. That means accurate readings without designing analog circuits. ESPHome supports it directly, and several modules can share one bus. This version (about 4.6 stars from 26 ratings) comes in a housing, which is important because one side connects to mains. Use the v3.0 Modbus protocol in your firmware. Only 6 were in stock when we checked.

CT clamps measure current by clipping around a single conductor, so you never cut a wire. The SCT-013-030 version (about 4.9 stars from 14 ratings) has a built-in burden resistor and outputs up to 1 V at 30 A, which makes it the easiest to connect to an ESP32 ADC: add a bias circuit (two resistors and a capacitor) to centre the AC signal at about half of 3.3 V, then sample it quickly and compute RMS current. Clamp it around one conductor only (live or neutral, not the whole cable), or the fields cancel out. 16 were in stock when we checked.

For main feeds and heavy circuits, the SCT-013-000 handles up to 100 A. Unlike the 030 version, it outputs a current (50 mA at full scale), so you must add a burden resistor sized for the ESP32’s 3.3 V range. Never leave a current-output CT open-circuit while it’s clamped on a live conductor, because it can develop dangerous voltages. This 4-pack (5.0 stars from 5 ratings) covers both legs of a split-phase supply plus two circuits. 11 were in stock when we checked.

For DC systems, such as a 12 V or 24 V solar battery, an e-bike pack or a van power system, the INA226 measures bus voltage up to 36 V and current through a shunt with 16-bit resolution, in both directions, so you can track charging and discharging. It talks I2C, works at 3.3 V, and has an alert pin for over-current warnings. For currents above the module’s onboard shunt rating, use it with an external shunt. 14 were in stock when we checked.

The INA219 (about 4.2 stars from 84 ratings) is the most widely used DC current sensor in the maker world. It’s perfect for measuring the ESP32’s own consumption: put it in the supply line and log how much current your project draws in active mode, Wi-Fi bursts and deep sleep, then estimate battery life. It handles up to 26 V and has libraries for every framework. For solar systems above 26 V, choose the INA226 instead. 14 were in stock when we checked.

Whole home, many circuits

The Emporia Vue 3 with circuit sensors.

Local data, no flashing

The Shelly Pro EM, or Pro 3EM for three phases.

One appliance

Shelly PM Mini Gen3, or EM Mini Gen4 for Matter.

DIY AC monitor

ESP32 + PZEM-004T, or SCT-013 clamps for current only.

Solar battery or van

ESP32 + INA226 with a shunt.

Why can’t I just measure current to get power?

Real power depends on voltage, current and the phase angle between them (power factor). A CT clamp alone gives you an estimate that assumes a fixed voltage and a power factor of 1, which is wrong for motors, chargers and many electronics. Meters like the PZEM-004T, Shelly and Emporia measure voltage too, so they report true power.

Is the ESP32’s ADC good enough for energy monitoring?

It works for rough current estimates with CT clamps, but it’s noisy and non-linear. For accurate results, use a dedicated metering IC that does the measurement and sends results over UART or SPI, as the PZEM-004T and the commercial monitors in this guide do.

Do these work with Home Assistant’s Energy dashboard?

Yes. Shelly devices integrate locally, the Emporia Vue works through ESPHome firmware or community cloud integrations, and DIY meters running ESPHome report energy sensors that plug straight into the Energy dashboard.

Can I install a whole-home monitor myself?

Rules vary by country, and working inside a panel is dangerous. Many regions require a licensed electrician for any work in the panel. If in doubt, have a professional fit the CT clamps and voltage connections; you can do the configuration afterwards.