SDM01 Gen2 / COMBO Compact Energy Meter

The SDM01 Combo Gen2 is the next-generation upgrade of the SDM01 Combo. It features ultra-fast bi-directional power measurement — making it significantly more responsive for export limiting and zero-export applications — along with support for larger CT sizes (up to 400A), updated CT aperture options (Ø10 / Ø16 / Ø24 / Ø36 mm), and an expanded local API for tighter HEMS integration. The core form factor remains the same compact 1-module (18mm) DIN-rail design.

Two main module variants are available on this store:

• Tuya Wi-Fi + RS485 (SDM01G2-TWM-\*) — Best for Tuya Smart / Smart Life app users and cloud-based energy dashboards.
• Standard Zigbee 3.0 + RS485 (SDM01G2-SZM-\*) — Best for local, cloud-independent setups such as Home Assistant, Homey, or other standard Zigbee hubs.

Both variants include an RS485 port for Modbus RTU wired communication, making them suitable for hybrid installations.Looking for the Tuya LAN+ version? There is also a Tuya LAN+ variant of the SDM01 Combo Gen2 that supports local LAN communication through Tuya's official ecosystem. This variant is not sold here — it is exclusively available under Tuya's official HEMS (Home Energy Management System) brand - Conow. Please contact them directly for availability.What about an Open Wi-Fi version? An Open Wi-Fi variant based on the ESP32-C6 module is currently in development and is planned for release by end of 2026. If you need open firmware flexibility today, the Standard Zigbee 3.0 variant with local API support may be a suitable alternative in the meantime.

The main module is powered and measures voltage through four wires connected to the voltage take-offs connector: X (L1), Y (L2), Z (L3), and N (Neutral). The device supports the following system configurations at 50/60 Hz:

• 120–240 VAC phase-to-neutral
• 208–415 VAC phase-to-phase

Beyond standard three-phase (3P4W) systems, the SDM01 Combo Gen2 also supports:

• Split-phase systems (e.g., 120/240V North American residential) — use two of the three CT channels for L1 and L2, with N as the neutral reference.
• Three independent single-phase circuits — each CT can monitor a separate single-phase branch circuit sharing a common neutral, making it a flexible multi-circuit monitor for mixed panel layouts.

⚠️ Note: The SDM01 Combo Gen2 is not suitable for 3P3W (three-phase, no neutral) installations.

Yes. Each CT has an arrow indicating the positive (forward) power flow direction — typically pointing toward the load side. The CT wires must also be connected with correct polarity: Red (+) to the "+" terminal and Black (−) to the "−" terminal on the CT connector. Reversed polarity will result in negative power readings but will not damage the device.

It depends on the variant:

• Standard Zigbee 3.0 variant ✅ — Integrates natively with Home Assistant via standard Zigbee coordinators, fully local and cloud-independent.
• Tuya Wi-Fi variant (sold here) ❌ — This variant operates within the Tuya cloud ecosystem and does not support direct Home Assistant integration. If Home Assistant compatibility is a requirement, we recommend the Zigbee variant instead.
• Tuya LAN+ variant (sold under Conow - Tuya's official HEMS brand) — Tuya is reportedly working on adding official Home Assistant API support for the LAN+ variant. For the latest status and timeline, please contact Conow directly.

Yes. The hybrid variants (Wi-Fi + RS485 and Zigbee + RS485) allow simultaneous use of both wireless and wired communication. This is particularly useful in industrial or commercial installations where Modbus RTU is required for integration with PLCs, SCADA systems, Inverters or EV charger controllers, while wireless connectivity is used for monitoring dashboards.

The SDM01 Combo Gen2 is certified to Class 1 per IEC 61557-12. However, "Class 1" does not mean the device is always accurate to ±1% under all conditions. The standard defines different uncertainty limits depending on the current range and power factor — and this applies to every Class 1 PMD on the market, not just the SDM01 Combo Gen2.

Per IEC 61557-12:2021, Table 8
Intrinsic uncertainty limits for active power and active energy (Class 1, C = 1):

• Current Range: 5%I_b ≤ I < 10%I_bPower Factor: 1 | Accuracy: ±1.5%
• Current Range: 10%I_b ≤ I ≤ I_maxPower Factor: 1 | Accuracy: ±1.0%
• Current Range: 10%I_b ≤ I < 20%I_bPower Factor: 0.5L / 0.8C | Accuracy: ±1.5%
• Current Range: 20%I_b ≤ I ≤ I_maxPower Factor: 0.5L / 0.8C | Accuracy: ±1.0%

Example — Applied to the SDM01G2 120A variant
(I_b = 20A, I_max = 120A):

• Light load (1A – 2A)Power Factor: 1 | Accuracy: ±1.5%
• Normal load (2A – 120A)Power Factor: 1 | Accuracy: ±1.0%
• Light load, reactive (2A – 4A)Power Factor: 0.5L / 0.8C | Accuracy: ±1.5%
• Normal load, reactive (4A – 120A)Power Factor: 0.5L / 0.8C | Accuracy: ±1.0%

The ±1.0% zone covers the vast majority of real-world operating conditions. The ±1.5% tolerance only applies at very light loads — below 2A for the 120A variant — which represents a small fraction of typical operating time in any residential or commercial installation.

📝 Note: The standard sets no accuracy requirement below 5%I_b at PF = 1, and below 10%I_b at non-unity PF. This is consistent across all IEC 61557-12 Class 1 devices.

Yes. Bi-directional measurement is a core feature of the SDM01 Combo Gen2. It simultaneously tracks imported energy (consumption from the grid) and exported energy (generation fed back to the grid), making it ideal for households and businesses with solar PV or battery storage systems.

Yes. The three CTs can be deployed across three separate single-phase circuits (e.g., three different branch circuits in a distribution board) rather than the three phases of a single three-phase load. This makes it a versatile multi-circuit monitor for mixed residential and light commercial panel layouts.

No. If a CT is damaged or needs replacement, simply order a replacement CT of the same official Bituo Technik model — no factory recalibration is required.

We tightly control the ratio error and phase error of every CT we produce, ensuring that any officially designated Bituo Technik CT of the same model is fully interchangeable with your SDM01 Combo Gen2 and will maintain Class 1 accuracy straight out of the box. This makes field maintenance and replacement straightforward, with no downtime waiting for factory service.

📝 Note: This interchangeability guarantee applies only to official Bituo Technik designated CTs of the matching model. Third-party or non-designated CTs are not covered and may affect measurement accuracy.