SunSpec Model 122 — Measurements_Status
SunSpec Model 122 is a standardized extended measurements and status block defined by the SunSpec Alliance for grid-tied inverters supporting PV, storage, or combined DER installations. This Modbus TCP template reads connection status flags for PV, storage, and ECP grid coupling, lifetime accumulated energy across all four reactive power quadrants, available active and reactive power headroom, active control mode bitmasks, inverter timestamp, ride-through status, and isolation resistance. Integrators using the ModbusCloud Gateway can track both lifetime yield and real-time operational state across any SunSpec-compliant inverter without vendor-specific customization.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 22, read only
- Brand
- SunSpec
- Last updated
Registers (22)
22 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| pvconn | Read | ||||
| storconn | Read | ||||
| ecpconn | Read | ||||
| actwh | Wh | Read | |||
| actvah | VAh | Read | |||
| actvarhq1 | varh | Read | |||
| actvarhq2 | varh | Read | |||
| actvarhq3 | varh | Read | |||
| actvarhq4 | varh | Read | |||
| varaval | var | Read | |||
| varaval_sf | Read | ||||
| waval | var | Read | |||
| waval_sf | Read | ||||
| stsetlimmsk | Read | ||||
| stactctl | Read | ||||
| tmsrc | Read | ||||
| tms | Secs | Read | |||
| rtst | Read | ||||
| ris | ohms | Read | |||
| ris_sf | Read |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor lifetime active energy output via actwh to verify yield against contractual guarantees over time.
- Track per-quadrant reactive energy counters to audit grid code compliance for Q management programs.
- Alert on changes in stsetlimmsk to detect when an inverter hits a power or reactive-power setpoint limit.
- Verify ecpconn and pvconn status flags after maintenance to confirm full grid reconnection before leaving site.
- Compare waval against rated capacity to spot inverter derating events caused by thermal or grid conditions.
Installation
Enable Modbus TCP on the inverter under the communication or Modbus section of its web interface, and note the assigned unit ID (commonly 1 or 126 depending on manufacturer).
Connect the inverter to the same LAN segment as the ModbusCloud Gateway, ensuring TCP port 502 is reachable and no firewall blocks the connection.
In the ModbusCloud portal, add a new device, import the SunSpec Model 122 template, and enter the inverter IP address and unit ID.
Read back registers id and l to confirm the model is present, then spot-check actwh to verify live data is flowing correctly.
Things to watch for
Why do actvarhq1 through actvarhq4 all read zero?
Many inverters only increment reactive energy quadrant counters when reactive power control is actively engaged. If the inverter runs at unity power factor with no Q setpoint active, all four quadrant accumulators will remain zero. Enable a reactive power mode in the inverter to confirm the registers respond.
The gateway connects but id and l return unexpected values. What now?
SunSpec models are discovered dynamically: the actual Modbus address of Model 122 is not fixed and depends on how many models precede it in the device map. The template uses relative offsets from the model header. If absolute addresses are used instead, reads will land in the wrong model. Confirm the template is configured for relative addressing starting at the model id register.
Isolation resistance register ris reads NaN or 65535. Is the sensor faulty?
A NaN value in ris is normal when the inverter does not support isolation resistance measurement or when the measurement is unavailable at night with no DC voltage present. Check the inverter datasheet to confirm whether Ris is implemented, and verify DC strings are energized before expecting a valid reading.
Timestamp register tms shows a value far in the past. What is wrong?
tms counts seconds since 2000-01-01 00:00 UTC. If the inverter clock has never been synchronized, it may report a very low count. Verify that the inverter time synchronization source shown in tmsrc is active and reachable. Correct timekeeping is important for aligning energy logs with external billing or monitoring systems.
Knowledge base articles for this device
SunSpec Modbus: one register map for many inverters
SunSpec Modbus is the open register map SMA, Fronius, SolarEdge and Kostal share. The layout, int+SF vs float, the TCP port per brand and reading a mixed fleet.
Fronius Modbus: read a Symo GEN24 over Modbus TCP
Fronius Modbus explained: enable Modbus TCP on the Symo GEN24 on port 502, choose between int+SF and float, read the right SunSpec registers and scale them correctly. Practical guide for solar installers.
SMA Modbus: reading a Sunny Boy over Modbus TCP (installers)
SMA Modbus explained: enable the Modbus TCP server on port 502, choose between the SMA profile (unit ID 3) and SunSpec (unit ID 126), read the right registers, and handle the NaN values at night. Practical guide for installers.
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