Refoss Smart Home Energy Monitor, Native Open API & Web UI (No Cloud Required)
Quick take
The Refoss EM16 is a circuit-level smart energy monitor designed for people who want local data access, native Home Assistant integration, and control without cloud dependency. It’s a strong fit for solar homes and anyone building automation around real-time appliance and circuit usage. The biggest buying caveat is that getting accurate, useful results takes upfront circuit planning, and the installation involves permanent clamp wiring inside your panel.
Pros and cons
Pros
- Local-first access via built-in web UI, Open API, and MQTT (no cloud requirement).
- Native Home Assistant support, with OpenClaw support for automation without firmware flashing.
- Circuit-level monitoring with 2 main circuit sensors (200A) plus 16 branch sensors (60A).
- Real-time measurements including voltage, current, active power, and power factor.
Cons
- Requires panel planning to choose which circuits go where (some circuits share options depending on L1/L2).
- Clamp wiring is hard to make “neat” in some breaker boxes, with fixed cable lengths noted by some installers.
- Setup can include calibration tweaks, since current direction or multipliers may need adjustment to match your panel wiring and app setup.
What buyers think
Buyer-review evidence highlights the EM16 as a capable whole-home monitor once installed, especially for people using Home Assistant. Multiple buyers mention straightforward setup and configuration inside the app, along with stable Wi-Fi behavior during everyday use. Installation experience is generally described as manageable for users comfortable working around breaker panels, with planning for which circuits to monitor repeatedly called out as important. Reviews also point to a common reality of clamp-on systems: cable routing can look messy depending on your panel, and getting readings aligned with your wiring sometimes takes app settings or helper configuration (like toggling direction or using multipliers) before the data matches expectations. Overall, review evidence suggests the product performs best when buyers take time to plan their monitoring goals (for example, solar self-consumption, specific high-load circuits, or automation targets) before they open the panel.
What the Refoss EM16 measures, and why it matters
The EM16 is built to measure electricity at a circuit level, not just total home energy. That lets you see how specific appliances and circuits behave throughout the day, then use that visibility for automation and alerts. Key measurements include voltage, current, active power, and power factor, which are useful for understanding both usage and the electrical characteristics of your loads.
It also supports an “automation around solar usage” style approach often described as reducing low-value export by prioritizing local consumption. Practically, that means you can build rules that react when solar production is high and shift suitable loads (for example EV charging or heat-related loads) to run at midday instead of during higher-price grid periods.
Local control, open integrations, and Home Assistant compatibility
A major differentiator here is local access. The system is designed so your energy monitor data is available locally through its built-in web UI, plus Open API and MQTT for integration. That can be appealing if you want to avoid cloud dependency, reduce reliance on internet uptime, or keep home automation logic running even when your internet connection is unstable.
Home Assistant integration is described as native, without requiring firmware flashing. For automation-focused buyers, that means less tinkering before you can bring the monitor into your dashboards and automations. The listing also references OpenClaw support for AI-driven automation use cases, which may interest people who want to build smarter rules based on energy data and device behavior.
Installation reality check (and who should plan ahead)
This is a clamp-on monitor for breaker panels, and installation is the part where buyers tend to spend the most time deciding what they want to measure. The EM16 supports two main circuit sensors (each rated for 2–200A) and sixteen branch sensors (each rated for 1–60A). Because of how sensors apply to your panel layout, you typically need to pick which circuits are worth monitoring and assign them thoughtfully before you start wiring.
Review evidence also indicates that cable management may not look tidy in all setups, since the sensor leads connect through fixed-length molded cabling. Some buyers are fine with this as part of the tradeoff for a kit, while others may prefer a cleaner internal routing solution and should evaluate their panel space and cable pathways ahead of time.
Finally, a recurring setup theme is that you may need to adjust for reading direction or multipliers so your data matches the actual flow in your panel. This is not unusual for clamp-based current monitoring. The difference is that the EM16 provides app-side controls to correct it, so you can align the readings without abandoning the setup.
Accuracy, history, and data export
The EM16 is positioned as accurate for meaningful energy tracking, with a ±1% accuracy claim at its typical measurement ranges, and ±2% at low current. It also stores daily data for up to five years and supports export, which is helpful if you want to review long-term trends or build your own analysis outside the app.
If your goal is practical bill reduction or identifying inefficient loads, longer history and export options matter more than minute-to-minute detail. Circuit-level monitoring can help you spot which devices or circuits are consuming power unexpectedly, and then set schedules or alerts to curb it.
Solar “zero feed-in” and peak management use cases
For solar homes, this monitor is designed to support automation that prioritizes local consumption. In plain terms, it’s meant to help you use more of your solar generation inside your home by triggering loads at times when surplus power is available. It also supports setting usage targets and receiving instant alerts when appliances exceed normal consumption on monitored circuits.
For peak management, you can use those alerts and automation features to adjust schedules (for example, shifting a washer, water heater, or EV charger to midday windows) and avoid higher-cost usage periods. The best results usually come when your circuit assignments reflect what you actually want to control.
Pros and cons recap
Best for
- Home Assistant users who want local-first monitoring with MQTT and Open API options.
- Solar households interested in automation that uses surplus power locally.
- Buyers who want circuit-level visibility for specific high-load appliances and targeted alerts.
Who should avoid it (or consider alternatives)
- DIY shoppers who are not comfortable planning circuit assignments and installing clamp sensors inside an electrical panel.
- Anyone expecting a “clean looking” internal cable layout, since fixed cable lengths may create visible wiring messiness in some panels.
- Buyers who want plug-and-play monitoring with no configuration. You may still need to confirm direction or multipliers for correct readings.
Verdict
The Refoss EM16 is a strong circuit-level energy monitor for buyers who value local data access and want deep home automation integration without relying on cloud services. It brings real-time power measurements, multi-circuit monitoring capacity, and solar-focused automation tools into one system. If you are willing to plan your circuits carefully and take a bit of time to verify your readings during setup, it can be a practical foundation for monitoring, alerts, and automation. If you want effortless installation and no post-setup tweaking, you may want to look at simpler monitoring options with fewer integration and configuration variables.
FAQs
Refoss EM16 smart energy monitor questions
Does the Refoss EM16 work without internet or cloud services?
Yes. It’s designed for local control and local access using its built-in web UI, Open API, and MQTT, with data stored locally so it does not rely on cloud services.
Does it integrate with Home Assistant without flashing firmware?
Yes. It’s presented as native Home Assistant integration, so you can add it without firmware flashing.
How many circuits can it monitor?
It supports 2 main circuit sensors (2–200A each) plus 16 branch sensors (1–60A each), giving you up to 16 circuit channels plus the two main sensors depending on your panel setup.
What does “zero feed-in” mean here?
Zero feed-in generally means using solar power inside your home first, rather than exporting surplus to the grid. You can use automation rules to prioritize running compatible loads when surplus solar is available.
Do I need to worry about correct reading direction?
Circuit current direction can affect how power values appear, so some buyers may need to adjust direction or multipliers in the app to ensure readings match your panel wiring. The setup tools are there to help align the data.
Is it accurate enough for real energy decisions?
The EM16 is marketed with ±1% accuracy in the specified 2–200A measurement range and ±2% at low current, which is intended to support meaningful monitoring and automation decisions.
Specifications
| Product Title | Refoss Smart Home Energy Monitor, Native Open API & Web UI (No Cloud Required), Real Time Electricity Usage Monitor, Power Consumption Meter Works with Home Assistant & MQTT, Solar Net Metering, ETL |
|---|---|
| Category | Tools & Home Improvement > Electrical > Home Automation Devices > Modules |
| Manufacturer | Refoss |
| Color | Orange+White |
| Item Weight | 4.27 pounds |
| Product Dimensions | 4.5 x 3.48 x 1.1 inches |
| Part Number | EM16 |
| Item model number | EM16 |
| Item Package Quantity | 1 |
| Included Components | Home Energy Monitor, WiFi Antenna Assembly, 200A Current Transformers x 2, 60A Current Transformers x 16, 3.5mm Insulation Plugs x 2, 2.5mm Insulation Plugs x 16, Wire Nuts x 3, Extra Wires x 3, Wire Harness, User Manual |
| Batteries Included? | No |
| Batteries Required? | No |
Available variants
Color
- Orange+White
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