FAQ
TL;DR: One MEW‑01 setup logged over 3 MWh and "agrees to the nearest 0.1 kWh"; newer firmware adds interphase balancing. This FAQ helps PV homeowners choose Shelly 3EM vs Zamel MEW‑01 for accurate sub‑metering. [Elektroda, xury, post #20115816]
Why it matters: You’ll pick a sub‑meter that fits your PV, billing model, and local HA/MQTT setup without surprises.
Quick Facts
- MEW‑01’s newer firmware adds interphase balancing; accuracy matched a PGE meter within 0.1 kWh over 3 MWh tracked. [Elektroda, xury, post #20115816]
- Shelly 3EM was available around €99 according to a buyer’s report. [Elektroda, marcingebus, post #19150087]
- Community pricing snapshot: Shelly 3EM and Zamel MEW‑01 both hovered near 530 PLN. [Elektroda, chemik_16, post #20115206]
- Shelly 3EM shows per‑phase usage; kit CTs ~100 A, 30 A CTs optional; neutral can be metered. [Elektroda, marcingebus, post #19558237]
- Cloud logging via Supli can miss data during internet outages, creating discrepancies. [Elektroda, kood, post #20115878]
How accurate is Zamel MEW‑01 compared with a utility meter?
A user recorded over 3 MWh production and 1.2 MWh consumption. MEW‑01 matched a PGE meter within 0.1 kWh. “More accuracy I can’t get from the PGE meter.” This setup used firmware with interphase balancing, suitable for PV self‑consumption tracking. [Elektroda, xury, post #20115816]
Does Zamel MEW‑01 support interphase balancing for PV/self‑consumption?
Yes. The newer MEW‑01 firmware provides interphase balancing, aligning readings more closely with utility meters in three‑phase homes. [Elektroda, xury, post #20115816]
Does Shelly 3EM do interphase balancing like my utility meter?
The thread confirms Shelly 3EM reports per‑phase values. Interphase balancing was not confirmed in that user’s report. If you need balancing, verify firmware notes before purchase. [Elektroda, marcingebus, post #19558237]
Can Shelly 3EM measure the neutral, and what CT options exist?
Yes. Shelly 3EM can meter the neutral conductor. The pack included ~100 A current transformers, with 30 A CTs available. It displays per‑phase consumption for detailed diagnostics. [Elektroda, marcingebus, post #19558237]
Will Zamel MEW‑01 Lite work with Home Assistant over MQTT?
Yes. A user confirmed seamless operation: “It works with HA without problems.” Use MQTT to keep data local and avoid cloud dependencies. [Elektroda, xury, post #20153877]
Can MEW‑01 work fully local without the cloud?
Yes. One setup runs MEW‑01 without cloud, using MQTT. PV production is read from the inverter via Node‑RED, reducing reliance on remote services. [Elektroda, xury, post #20115816]
What happens if the internet drops while using the Supli cloud?
Readings can show gaps. The cloud did not count data during outages, causing discrepancies versus the Tauron meter. Consider local MQTT to preserve continuity. [Elektroda, kood, post #20115878]
How do I read my PV inverter locally with ESPHome?
- Wire the inverter’s RS485 to a reliable RS485‑to‑TTL converter.
- Flash an ESP8266 with ESPHome and configure the RS485 UART.
- Define sensors, choose a suitable polling interval, and publish to Home Assistant.
This approach delivered stable automation signals. [Elektroda, kood, post #20115929]
How fast can I poll inverter data versus the vendor cloud?
A Node‑RED flow queried an LSW‑3 logger every two seconds. The vendor cloud polled roughly every five minutes. Faster local polling improves automation responsiveness. [Elektroda, xury, post #20115940]
Is SDM630 a good alternative to Shelly 3EM or MEW‑01?
Yes for many users. SDM630 is cheaper, uses no external CTs, and has a built‑in display. The user also noted standards compliance and no measurement complaints. [Elektroda, chemik_16, post #20115827]
Where should I place sub‑meters in a smart PV home?
One plan used three meters: at the grid input, at a PC circuit, and before the PV inverter. This layout separates import, critical loads, and generation. [Elektroda, marcingebus, post #19150087]
What practical insights did Shelly 3EM provide in real homes?
Per‑phase views helped diagnose loads. A user spotted when a heat pump enabled backup heaters in comfort mode. “To my eye it is Git.” [Elektroda, marcingebus, post #19558237]
How much do Shelly 3EM and Zamel MEW‑01 cost?
A snapshot showed both near 530 PLN, with a slight preference for Shelly due to dimensions. Always check current pricing and availability. [Elektroda, chemik_16, post #20115206]
What hardware is inside Shelly 3EM? Is Tasmota possible?
A teardown link indicated an ADE7880 metering IC and ESP8266 MCU. The community discusses Tasmota for this platform in detail. [Elektroda, chemik_16, post #20115206]
Does MEW‑01 Lite support vector (phase) counting?
A user selected MEW‑01 Lite noting it as the only option with vector counting for his constraints, and planned to test. [Elektroda, chemik_16, post #20116920]
Do I need more than one sub‑meter for PV monitoring?
Not necessarily. One meter can suffice if you read PV production separately, for example from the inverter via logger and MQTT. [Elektroda, xury, post #20115816]
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via NodeRed thanks to a flow from a colleague starob .
