
Modbus TCP
SunSpec Model 126 — Static Volt-VAR
SunSpec
Overview
SunSpec Model 126 is an open interoperability standard for static Volt-VAR control on grid-tied inverters and distributed energy resources. This Modbus TCP template covers the model header registers, curve selection and enable controls (actcrv, modena), timing registers (wintms, rvrttms, rmptms), and the read-only capability descriptors (ncrv, npt) together with their three scale-factor registers (v_sf, deptref_sf, rmpincdec_sf). Any SunSpec-compliant inverter implementing Model 126 can be connected to the ModbusCloud Gateway and monitored or configured from your portal without manual register mapping.
Use cases
- Verify that the correct Volt-VAR curve is active after a grid-code change by polling the actcrv register in your dashboard.
- Monitor the modena enable flag across multiple sites to confirm Volt-VAR mode has not been inadvertently disabled during maintenance.
- Track the rvrttms reversion timeout setting to ensure automatic fallback to the default curve is configured per utility requirements.





