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A SIX-CHANNEL OPEN-SOURCE ENERGY METER SHOWS WHICH CIRCUIT IN THE HOUSE IS ACTUALLY EATING THE BILL

This board turns a breaker box into a live per-circuit power graph that runs inside the house.

by CircuitSetup

FULL CAD BOM FIRMWARE DOCS

EnergyHome

difficulty
●●●●○
time
a weekend
license
MIT
repo
repo ACTIVE686 stars

WHAT YOU’LL NEED

  • 3D printer + filament — printable parts — files are in the repo
  • Electronic parts — full list with part numbers in the repo BOM
  • Dev board / microcontroller — runs the project firmware

Partner

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Videos
1

COMPAREE VERDICT

The Expandable 6-Channel ESP32 Energy Meter is the open hardware answer to knowing which circuit in the house is actually eating the bill. Two ATM90E32AS metering chips give 16-bit resolution with around 0.1 percent typical accuracy, reporting active power, reactive power, apparent power, power factor, frequency and temperature. Six current channels sit on the main board and up to six add-on boards stack for 42 channels total, which covers every breaker in a normal consumer unit. Current is picked up by clip-on current transformers that clamp around the existing wiring rather than cutting into it. The board needs an ESP32 development board plus a 9 to 12 volt AC-AC adapter — not a DC one — because it samples the mains waveform for the voltage reference. Firmware options are ESPHome (project recommended), Home Assistant, EmonESP with emonCMS, and CircuitPython or MicroPython libraries. The result is a live per-circuit graph on a dashboard that never leaves the owner's network. The single biggest trap: this is not a kit. The board must be ordered from a PCB house or bought assembled from CircuitSetup, the current transformers must be sourced separately, and opening a live consumer unit is regulated electrical work in most places. The project is for someone who already knows their way around mains wiring or is prepared to pay an electrician to fit the clamps. For that person, this is the only open hardware meter that scales past a handful of circuits.

NOT IN THE REPO

  • —Hardware files (KiCAD), Gerbers, and assembly instructions are in the repository under MIT licence, which permits commercial use.
  • —Firmware is ESPHome (recommended), with support for direct Home Assistant integration, EmonESP with emonCMS, CircuitPython and MicroPython.
  • —The board itself must be ordered from a PCB house or bought assembled from CircuitSetup — no pre-made kit.
  • —Current transformers, the ESP32 development board, and the 9-12 V AC-AC adapter are not included and must be sourced separately.
  • —Opening a live consumer unit is regulated electrical work in most jurisdictions, even though the clamps themselves never touch conductors.
  • —The 0.1 percent accuracy figure is the project's stated typical value, not an independent measurement.

Can I build this?

Printnothing required
BuyPCB (order Gerbers or buy assembled from CircuitSetup), ESP32 development board, clip-on current transformers (SCT-013-000 or equivalent, one per circuit), 9-12 V AC-AC adapter, add-on boards if monitoring more than six circuits
Toolssoldering iron if assembling the board yourself, screwdriver for DIN rail mount, Home Assistant or emonCMS server for data display, electrician if not qualified for mains work
Skillsintermediate electronics assembly if ordering bare PCBs, familiarity with ESPHome or Home Assistant, comfortable working near (not on) live mains or willing to hire an electrician
Timea weekend to assemble and configure, plus electrician time if required
Cost$$ — dominated by the assembled board if bought from CircuitSetup (around $70-90 for the main 6-channel), current transformers (around $10-15 each), and electrician call-out if needed
SafetyOpening a live consumer unit is regulated electrical work in most countries. The current transformers themselves never touch conductors, but fitting them requires the panel to be open. If not qualified, hire an electrician.

This build involves mains voltage — for adults comfortable with electrical work only.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

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Videos

Six-channel energy meter install and dashboard

No official project video. Community walkthroughs exist but are not linked in the repository.

Gallery

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Check local regulations on who may open a consumer unit(In most jurisdictions this is restricted electrical work, even though the clamps themselves are non-invasive.)
  2. 2.Order or buy the main board (Gerbers are in the Hardware folder. Assembled boards are available from circuitsetup.us.)
  3. 3.Source current transformers (SCT-013-000 100 A / 50 mA CTs are the common choice. One per circuit.)
  4. 4.Flash ESPHome firmware (ESPHome YAML config is in the repository. Alternative firmware options are also documented.)
  5. 5.Fit the clamps and connect to Home Assistant or emonCMS(If not qualified for mains work, this is where the electrician comes in.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

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KNOWN ISSUES

  • The board requires a 9-12 V AC-AC adapter, not a DC one — the project samples the mains waveform for its voltage reference and a DC adapter will not work.
  • Current transformers are not included. SCT-013-000 100 A / 50 mA CTs are the common choice, but the project supports others — check the documentation before ordering.
  • Opening a live consumer unit is regulated work in most places, even though the clamps themselves never touch conductors. Budget for an electrician if not qualified.
  • The 0.1 percent accuracy is the project's stated typical value for the ATM90E32AS chips, not an independent calibration — real-world accuracy depends on CT quality and placement.
  • There is no official pre-made kit. The board must be ordered from a PCB house (Gerbers are in the repo) or bought assembled from CircuitSetup.
  • Home Assistant or emonCMS is expected — the firmware pushes data but does not include a built-in dashboard.

Can I monitor a three-phase supply?

Yes. Each ATM90E32AS chip can monitor three voltages and three currents, and the board has two chips. The ESPHome config includes examples for split-phase and three-phase setups.

Do I need to cut or splice any wiring?

No. The current transformers are clip-on clamps that hug the existing cable. Nothing is cut, but the panel must be open to fit them.

Can I use a different ESP32 board?

Yes, as long as it has the correct pin headers. The project uses a standard ESP32 DevKitC form factor.

What is the difference between this and a whole-house monitor?

A whole-house monitor gives one number for the entire property. This gives one number per circuit, which is what turns a vague bill into a list of named appliances.

Can I stack more than six add-on boards?

The project states up to six add-on boards for 42 channels total. Beyond that, the I2C bus or power supply may become a limitation.

Community builds

No community builds yet — be the first, we feature the best ones.

Discussion1

FROM THE COMPAREE TEAM

Six channels on the main board, 42 if you stack the add-ons — and the whole thing runs ESPHome locally. Which circuit would you monitor first?

CompareeTEAM19d ago

Practical notes from our verification: the repository is active and well-documented, with clear assembly instructions and multiple firmware options. The project recommends ESPHome but supports Home Assistant, emonCMS, CircuitPython and MicroPython. The single biggest decision is whether to order bare PCBs and assemble, or buy the board assembled from CircuitSetup — the Gerbers are in the repo and the licence permits commercial manufacture, but sourcing the ATM90E32AS chips and doing the SMD assembly yourself is not trivial. The current transformers are standard SCT-013-000 types and widely available, but they are not included. Opening a consumer unit is regulated work in most countries, and that is the step most likely to require an electrician, even though the clamps themselves never touch conductors.

CircuitSetup

CircuitSetup is a US-based open hardware developer focused on energy monitoring and home automation. The Expandable 6-Channel ESP32 Energy Meter grew out of the need for a scalable, open solution that could monitor every circuit in a consumer unit without sending data to a third party.

GitHub Web

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
GitHub repo