SunSpec Model 120 — Nameplate
SunSpec Model 120, titled Nameplate, is a vendor-neutral information model defined by the SunSpec Alliance for Distributed Energy Resources. The template reads device identity and static nameplate ratings via Modbus TCP, covering continuous active power (wrtg), apparent power (vartg), per-quadrant reactive power limits (varrtgq1 to varrtgq4), current rating (artg), per-quadrant power factor (pfrtgq1 to pfrtgq4), energy capacity (whrtg), charge capacity (ahrrtg), and maximum charge and discharge rates (maxcharte, maxdischarte). Every measured value is paired with a SunSpec scale factor register. Knowing these nameplate figures lets you cross-check live readings against design limits across any compliant inverter or storage device.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 27, read only
- Brand
- SunSpec
- Last updated
Registers (27)
27 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| dertyp | Read | ||||
| wrtg | W | Read | |||
| wrtg_sf | Read | ||||
| vartg | VA | Read | |||
| vartg_sf | Read | ||||
| varrtgq1 | var | Read | |||
| varrtgq2 | var | Read | |||
| varrtgq3 | var | Read | |||
| varrtgq4 | var | Read | |||
| varrtg_sf | Read | ||||
| artg | A | Read | |||
| artg_sf | Read | ||||
| pfrtgq1 | cos() | Read | |||
| pfrtgq2 | cos() | Read | |||
| pfrtgq3 | cos() | Read | |||
| pfrtgq4 | cos() | Read | |||
| pfrtg_sf | Read | ||||
| whrtg | Wh | Read | |||
| whrtg_sf | Read | ||||
| ahrrtg | AH | Read | |||
| ahrrtg_sf | Read | ||||
| maxcharte | W | Read | |||
| maxcharte_sf | Read | ||||
| maxdischarte | W | Read | |||
| maxdischarte_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
- Verify that the active power rating reported by wrtg matches the device datasheet after initial commissioning.
- Compare per-quadrant reactive power limits (varrtgq1 to varrtgq4) against grid-code requirements at each site.
- Monitor the rated energy capacity (whrtg) of a battery-backed DER to track whether the manufacturer rating is correctly advertised over Modbus.
- Alert when maxcharte or maxdischarte reads zero, indicating the storage profile is not loaded or the device reports no storage capability.
- Audit apparent power rating (vartg) versus active power rating (wrtg) to confirm the inverter power factor operating envelope for each installation.
Installation
Enable Modbus TCP on the DER device through its web interface or commissioning tool, under the communication or Modbus section, and note the TCP port (typically 502) and unit ID.
Connect the DER device to the same Ethernet network as the ModbusCloud Gateway, confirming the device IP is reachable from the Gateway before proceeding.
In the ModbusCloud portal, add the Gateway, import the SunSpec Model 120 Nameplate template, and set the target IP address, port 502, and the unit ID assigned to the DER device.
Trigger a manual poll and verify that wrtg and vartg return non-zero values consistent with the device nameplate; confirm scale factors (wrtg_sf, vartg_sf) are applied correctly in the portal register table.
Things to watch for
Why do wrtg or vartg read zero or 65535?
A value of 65535 (0xFFFF) is the SunSpec not-implemented sentinel. This means the device does not populate that register for its DER type. For pure PV inverters, whrtg, ahrrtg, maxcharte, and maxdischarte are commonly not implemented and will return 65535. Treat these as absent, not as a communication fault.
My calculated wattage is orders of magnitude wrong. What is the cause?
SunSpec uses signed 16-bit scale factor registers (wrtg_sf, vartg_sf, etc.). The true value is the raw register multiplied by 10 raised to the power of the scale factor. A scale factor of -2 means divide the raw value by 100. If your integration ignores scale factors, all readings will be incorrectly scaled. Confirm your portal template applies each _sf register to its associated measurement.
The gateway connects but the dertyp register shows an unexpected value.
The DERTyp enumeration is vendor-defined within the SunSpec framework. A value of 4 typically indicates a PV inverter, while other values represent wind, storage, or hybrid types. If your device returns an unexpected value, consult the device Modbus documentation for its specific DERTyp mapping before assuming a communication error.
Register addresses in my poll tool do not match the template. Why?
SunSpec Model 120 uses relative block offsets, not absolute Modbus addresses. The actual register addresses depend on where the device places the model in its holding register map, which can start at base address 0, 40000, or 50000. The template uses offsets 0 to 26 relative to the model block start. Configure the correct base address in the ModbusCloud Gateway settings to align the template.
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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