The gateway connects but power_a and power_b always read zero.

Zero values on both power registers usually mean the inverter is in standby or the grid port is idle. Confirm the inverter is in normal on-grid operating mode and that PV or load is active. If values remain zero under load, verify the unit ID in the portal matches the slave address shown in the inverter's communication menu.

Why do I get a Modbus exception or timeout on function code 4?

Growatt hybrid inverters require a minimum gap of 850 ms between consecutive Modbus commands. If your polling interval is shorter than this, the inverter will drop requests or return an exception. Set the ModbusCloud Gateway poll interval to at least 1 second for this device to avoid communication errors.

The energy register value looks too large or jumps unexpectedly after a restart.

The energy register is a 32-bit unsigned cumulative counter that persists across restarts. The raw value may be a scaled integer; check the inverter's display readout against the register value to confirm the expected scaling factor documented in the Growatt Protocol II specification. Do not reset or compare absolute values across different inverter units.

RS485 wiring is connected but the portal shows no data at all.

On Growatt SPH hybrid models, set the RS485 interface mode to VPP in the inverter configuration and use the RS485-1 port. Confirm A and B lines are not swapped: reversed polarity is the most common cause of silent failures. Also check that no other Modbus master is polling the same bus simultaneously, as bus contention will block all communication.

Free Modbus template: Growatt Hybrid Inverter (grid)

The Growatt Hybrid Inverter is a grid-tied hybrid PV inverter that combines solar generation, battery storage, and grid interaction in a single unit. This Modbus RTU template reads three input registers from the grid port: two instantaneous power readings (power_a and power_b) and a cumulative energy counter (energy). Together these registers give installers and asset managers a continuous view of power flow and total energy throughput at the grid connection point. Connecting the Growatt Hybrid Inverter to ModbusCloud Gateway takes under ten minutes and immediately populates dashboards with live grid data.

Name	Address	Function	Type	Unit	Access
power_a Grid port power reading A, instantaneous watts at grid connection.	1021	FC04	uint32	W	R
power_b Grid port power reading B, second instantaneous watts measurement.	1029	FC04	uint32	W	R
energy Cumulative grid energy counter, total watt-hours through grid port.	1046	FC04	uint32	Wh	R