Why do I get zero or no response on register 5030 at night?

The Sungrow SG inverter powers down its communication interface when PV voltage is insufficient, typically at dusk and before dawn. A zero or timeout response at night is normal. Schedule your polling interval to accept zero values outside solar hours rather than treating them as errors.

Power values look wrong or inconsistent. What could cause this?

The Sungrow SG series stores U32 values in little-endian word order for double-word registers. If your Modbus client uses big-endian word order by default, the two 16-bit words will be swapped, producing a nonsensical large number. Ensure your client swaps the word order (little-endian) when assembling the 32-bit value from address 5030.

The gateway connects but no register values appear in the portal. What now?

Confirm the WiNet-S or LAN dongle is online and that port 502 is reachable from the ModbusCloud Gateway (use a port scan or ping test). Also verify the unit ID matches the inverter setting, which defaults to 1. Some older firmware versions require the dongle to be power-cycled after a network change before Modbus responds.

Daily energy register 5003 resets unexpectedly. Is that normal?

Yes. Register 5003 holds the daily yield and resets to zero at midnight local inverter time. If your portal shows a drop to zero mid-day, check that the inverter's internal clock is set correctly. A wrong system time on the inverter causes an off-schedule reset.

Free Modbus template: Sungrow SG Series Inverter (pv)

The Sungrow SG Series Inverter is a grid-connected PV string inverter designed for residential and small commercial solar installations. This Modbus TCP template reads two core registers: instantaneous AC output power (address 5030) and the daily energy yield (address 5003). With these two readings in your ModbusCloud portal you can track live generation output and log daily production totals, giving installers and site owners a clear, timestamped record of inverter performance without manual data collection.

Name	Address	Function	Type	Unit	Access
power Instantaneous AC active power output of the inverter, in watts.	5030	FC04	uint32	W	R
energy Daily PV energy yield, accumulated since midnight reset.	5003	FC04	uint32	Wh	R