Whole-home energy monitoring in Home Assistant (CT clamps)

The electricity bill tells you what happened. A CT monitor tells you who did it. Bring the mains and your busiest circuits into Home Assistant, and the mystery becomes a graph: the background load, the AC starting up, the appliance that never quite goes to sleep. Choose Shelly Pro 3EM 120A v2 for a matching whole-home installation, Refoss EM16P for a circuit-by-circuit view, or Shelly EM Gen3 to start with one circuit.

Research guide: hardware details come from the makers; setup comes from Home Assistant and the linked integration projects.

Quick picks: follow the watts you care about

Best local whole-home: Shelly Pro 3EM 120A v2. Its native Home Assistant integration, Ethernet connection and three included 120 A CTs make it the straightforward choice when its ratings and phase arrangement fit your service.

Best circuit-level: Refoss EM16P with 16 branch sensors. Get mains readings alongside individual circuits. The important setup detail: this current model uses the maker’s Refoss RPC custom integration, rather than Home Assistant’s built-in Refoss integration.

Single-circuit starter: Shelly EM Gen3 with one 50 A CT. Start small: monitor one suitable circuit, then add a compatible second clamp when another circuit earns your curiosity. This is the smaller-scope pick, rather than a whole-panel bundle.

Choose Shelly Pro EM-50 for two single-phase circuit channels with Ethernet and two included 50 A CTs. Choose Emporia Vue 3 when you want its cloud app or actively want an ESPHome hardware project; stock firmware takes a different route from the local-first picks.

Monitor and selected bundle	What it measures	Network	Home Assistant route	Best fit
Shelly Pro 3EM 120A v2	Three channels; 3 × 120 A CTs included	Ethernet / Wi-Fi	Built-in Shelly, Local Push	Whole-home monitoring on a matching service
Shelly EM Gen3	Two single-phase channels; 1 × 50 A CT included	Wi-Fi	Built-in Shelly, Local Push	Starting with one circuit
Shelly Pro EM-50	Two single-phase channels; 2 × 50 A CTs included	Ethernet / Wi-Fi	Built-in Shelly, Local Push	Two circuits with wired networking
Refoss EM16P	2 × 200 A main CTs + 16 × 60 A branch CTs	Wi-Fi	Maker’s custom Refoss RPC, Local Push	Mains plus detailed circuit breakdown
Emporia Vue 3, EMV3A-2P-16	Mains plus 16 branch sensors	Wi-Fi	Stock: cloud/custom integration; local: ESPHome reflash	Emporia app users or hardware tinkerers

These are alternative routes, not five things to buy. The Parts lists give you the exact configurations for each.

Start with the panel plan

Have an electrician install CT clamps inside the panel.

Before the appointment, decide whether you want the whole-home total, individual circuits, or both. Ask for the service type, current rating and proposed monitor location to be matched to the maker’s installation requirements. A 120 A CT and a 200 A service are different ratings; extra channels don’t change that.

The Pro 3EM v2 documentation covers single- and three-phase arrangements. The EM Gen3 and Pro EM-50 are single-phase, two-channel meters. Two channels alone don’t make either one a universal kit for the two legs of a US split-phase service.

For the EM Gen3, Shelly’s bundle FAQ confirms one 50 A clamp included, with a second compatible clamp purchased separately. Put the intended circuits on your shopping notes so a missing clamp doesn’t become the final surprise.

Ask the installer to label the channels. “Main import,” “AC circuit” and “washer circuit” are much more useful dashboard names than a row of unexplained channel numbers. Include solar/export in the plan if you have it: consumed energy and returned energy belong in separate readings.

Connect the monitor locally

Shelly: the cleanest built-in route

Home Assistant classifies its Shelly integration as Local Push: the device talks directly to Home Assistant without needing Shelly Cloud. Once the monitor is on your network, open Settings → Devices & services, accept its discovery card or choose Add integration → Shelly, and follow the prompts.

Open the device page and find its power and energy entities. Power in watts is what is happening now; energy in kWh is the amount used over time. Keep the native Shelly integration for this guide’s energy setup, even if the product also advertises Matter.

Refoss: EM16P is a different integration from EM16

The selected Refoss listing identifies EM16P. Its maker page documents offline operation, local web access, Open API and MQTT without cloud registration. For Home Assistant, follow the maker-maintained Refoss RPC installation guide: install Refoss RPC through HACS, restart Home Assistant, then add Refoss RPC under Settings → Devices & services. The project requires Home Assistant 2025.2.5 or newer and lists EM16P support across firmware versions.

Already own an older monitor? Home Assistant’s built-in Refoss integration is Local Polling and lists EM06 firmware 2.3.8 or newer and EM16 firmware 3.1.7 or newer. Those requirements describe EM06/EM16, not the EM16P sold in the selected bundle. Match the model first and the setup path becomes much easier.

Emporia Vue 3: cloud or tinkering

Emporia’s own explanation is clear: stock Vue firmware sends readings to the Emporia cloud and offers no direct local API. There is no core Home Assistant integration. The community HA Emporia Vue integration uses Emporia’s cloud API; Emporia’s developer page points to it as a community alternative.

For offline use, the emporia-vue-local project supports Vue 2 and Vue 3 with unofficial ESPHome firmware. That means opening the hardware and using programming tools, rather than enabling a setting in the app. Pick Vue for its cloud experience or because you want that conversion project. Pick Shelly for the simpler built-in local route.

Add it to the Energy dashboard

Get a working device page first, then give the readings a home:

1. Open Settings → Dashboards → Energy.
2. Under Electricity grid, select Add grid connection.
3. Select the statistic representing energy consumed from the grid. Use the monitor’s accumulated import energy, rather than an instantaneous watt reading.
4. Add the returned-to-grid statistic if you have an export measurement, then save the grid connection.
5. Add the branch-circuit energy sensors under Individual devices so they explain the whole-home total.
6. Watch the readings through a normal appliance cycle and compare channel labels with the installer’s notes.

Those are the current steps in Home Assistant’s grid-energy guide. Don’t add both the mains and all the branches as separate grid imports: the branch loads are already inside the mains reading.

For Refoss RPC, select the cumulative import sensor appropriate to the channel; the integration exposes lifetime totals when the device supplies them. Avoid choosing an arbitrary daily or weekly counter just because its name contains “energy.”

If a sensor is missing from the picker, use the Energy FAQ to check its units, energy device class, state class and recording. Prefer an existing compatible energy total. A power-only device can use the documented integration helper to accumulate energy. The individual-device guide also explains upstream devices, useful when a smart plug sits inside a circuit you already monitor.

Three projects that make the graphs useful

1. Meet your always-on baseline

Look at the whole-home power graph during a quiet period when the big loads are idle. That lower band is the interesting bit: everything that keeps sipping electricity while the headline appliances are taking a break.

Use branch readings to find the busiest contributors, then a local energy-monitoring smart plug or plug-in power meter to narrow a circuit down to an appliance. Leave essential equipment running; hunt discretionary loads first.

The following examples assume a constant draw, 24 hours a day for 30 days, at an assumed $0.15/kWh. They illustrate scale, not measured household loads or promised savings.

Assumed constant baseline	Energy over 30 days	Cost at assumed $0.15/kWh
100 W	72 kWh	$10.80
200 W	144 kWh	$21.60
300 W	216 kWh	$32.40

The arithmetic is watts ÷ 1,000 × hours × tariff. For a varying load, use accumulated kWh instead of stretching one moment’s watts across the month. Our always-on running-cost guide walks through that distinction.

2. Give the heat pump or AC a runtime scoreboard

Start with the dedicated circuit’s power history. Find the difference between standby and active operation, then create a Threshold helper under Settings → Devices & services → Helpers → Create helper. Select the circuit’s power sensor and set an Upper limit between the observed idle and running levels. Use Hysteresis to stop small fluctuations flickering the helper on and off.

Add a History Stats helper for that helper’s on state, using the time type and a period covering today. Now you have hours above your chosen running threshold alongside the circuit’s kWh. Watch how the pattern changes with weather or a thermostat adjustment.

Call it circuit-active time: variable-speed equipment, fans and standby loads can blur the boundary with actual compressor runtime. The power graph helps you tune the threshold, and kWh tells you how much energy the whole circuit used.

3. Put a monthly cost card where you’ll see it

Create a Utility Meter helper from your cumulative grid-import energy sensor, with a Monthly reset cycle. The first month starts when you create it; the next calendar month gives you a full cycle.

Then add a Markdown card to a dashboard. In its code editor, use this example and replace sensor.monthly_grid_import with the entity ID of your new helper:

type: markdown
title: Electricity this month
content: >-
  {% set kwh = states('sensor.monthly_grid_import') | float(none) %}
  {% if kwh is not none %}
  **{{ kwh | round(1) }} kWh** · **{{ '%.2f' | format(kwh * 0.15) }} USD**
  {% else %}
  Waiting for energy data.
  {% endif %}

The example card assumes $0.15/kWh: 300 kWh would display $45.00 before fixed charges and taxes. Replace 0.15 with your own flat electricity rate. For time-of-use billing, use the Utility Meter’s documented tariff setup and calculate each tariff separately.

The card waits when its source is unavailable rather than showing a fake zero. You get a useful spending estimate next to the live energy total, without confusing a mid-month reading with a full-month forecast.

Start with one useful question

Choose Pro 3EM v2 for a matching whole-home service, EM16P for the circuit breakdown, or EM Gen3 for a focused first circuit. Pro EM-50 adds wired networking to the two-channel route; Vue suits the cloud app or a deliberate ESPHome project.

Then ask one question: “What keeps this baseline up?” or “How much energy did the AC circuit use today?” Answer that before adding another graph. Head back to the Home Assistant hub for your next project, or use the starter kit to turn the rest of your sensor data into useful automations.

Only need one appliance’s reading rather than a panel view? Our Shelly retrofit guide compares a plug, a dry-contact relay and a meter-only Mini.