TapHome

Fronius Symo Solar Inverter

Modbus TCP
Submitted by
Last updated: 03. 2026
Fronius Symo Solar Inverter

The Fronius Symo is a 3-phase string inverter (3.0–8.2 kW) from the SnapINverter generation. TapHome connects to the inverter via Modbus TCP through the built-in Fronius Datamanager – no additional gateway or hardware is required.

The template reads SunSpec int+SF registers (Models 101/102/103 and MPPT Extension Model 160) and provides real-time AC power output, cumulative lifetime energy production, inverter operating state, and per-string DC power for up to two PV strings. An initialization script automatically sets the SunSpec Model Type to int+SF on first connection.

Network connection

The Fronius Datamanager provides the Modbus TCP interface. It is either built into the inverter or installed as a plug-in card. Communication uses standard Ethernet (wired or WiFi) on the same local network as TapHome Core.

  • Protocol: Modbus TCP (SunSpec Alliance)
  • Port: 502 (default)
  • Slave ID: 1 (for inverter #01; inverter #00 maps to Modbus ID 100)
  • SunSpec Model Type: int+SF (configured automatically by the template initialization script)

The TapHome template uses int+SF (integer with scale factor) register addresses, not the default float model. The template includes an initialization script that automatically switches the SunSpec Model Type to int+SF on first connection. If the initialization fails (e.g., due to a timeout), the model type must be changed manually in the Fronius Datamanager web interface. Using the wrong model type will result in incorrect or no readings.

Configuration

Enabling Modbus communication

Modbus TCP is disabled by default on the Fronius Datamanager. Follow these steps to enable it:

Fronius Datamanager 1.x (SnapINverter):

  1. Open a web browser and navigate to the Fronius Datamanager IP address (found under System Information in the web interface, or check the router’s DHCP lease table)
  2. Click Settings in the right sidebar
  3. Open the Modbus menu item
Fronius Datamanager web interface — Settings > Modbus menu
  1. Set Datenausgabe uber Modbus (Data output via Modbus) to tcp
  2. Configure the following settings:
Fronius Datamanager Modbus TCP settings — port, SunSpec model type, inverter control
SettingValue
Modbus Port502 (default)
Sunspec Model Typeint+SF (change from default float)
Wechselrichter-Steuerung uber ModbusEnable if write access is needed
  1. Click the checkmark button to save the settings

Fronius GEN24 / newer inverters:

  1. Open the inverter’s web interface (navigate to its IP address)
  2. Go to Communication > Modbus
  3. Set data output to tcp and SunSpec Model Type to int+SF
Import parameters

When importing the template in TapHome, provide:

  • IP Address – the Fronius Datamanager’s IP on the local network
  • Slave ID – Modbus device address (default: 1 for inverter #01; inverter #00 maps to Modbus ID 100)

Assign a static IP address or DHCP reservation to the Fronius Datamanager in the router settings to prevent the address from changing after a power cycle.

SunSpec register addresses are not constant – they depend on the SunSpec register list composition. The template assumes the default int+SF configuration. Firmware updates that add or remove SunSpec models may shift register addresses.

Device capabilities

Inverter operating state

Operating State is a read-only multi-value switch showing the current SunSpec operating state from the MPPT Extension Model (register H:40290). The inverter reports one of eight standard SunSpec states:

ValueStateDescription
1OffInverter is off
2In OperationAuto-shutdown (no solar irradiance)
3Run-up PhaseStarting up
4Normal OperationMPPT tracking – normal solar production
5Power ReductionThrottled by grid operator or settings
6Shutting DownSwitch-off phase
7FaultError exists – check inverter display
8StandbyStandby mode
Solar production monitoring

PV Production is an electricity meter device that provides two readings:

  • Current Power (H:40107) – real-time AC power output in kilowatts. The register value in watts is divided by 1000 for display in kW.
  • Total Energy (H:40101) – cumulative lifetime energy production in kilowatt-hours. The register value in watt-hours is divided by 1000 for display in kWh.

Two device-level service attributes are available on the PV Production device:

  • Frequency (H:40093) – AC grid frequency in Hz, rounded to integer
  • Maximum AC Current Capability (H:40143 with scale factor H:40144) – maximum rated AC current output
DC string power

The template monitors DC power from individual PV strings via the MPPT Extension Model 160:

  • String 1 (H:40284) – DC power from PV string 1 in watts, using the shared DC power scale factor (H:40267)
  • String 2 (H:40304) – DC power from PV string 2 in watts, using the same shared scale factor

On inverters with a single DC input, String 2 returns an unsupported value. On Hybrid systems, String 1 represents the PV input and String 2 represents storage.

Service diagnostics

The module exposes nine service attributes for identification and diagnostics:

  • Manufacturer (H:40004) – inverter manufacturer string
  • Device Model (H:40020) – inverter model string
  • Datamanager FW Version (H:40036) – Fronius Datamanager firmware version
  • Inverter SW Version (H:40044) – inverter software version
  • Serial Number (H:40052) – inverter serial number
  • Phase Configuration (H:40069) – Single Phase, Split Phase, or Three Phase
  • ECP Connection Status (H:40195) – Energy Communication Platform connection status (Disconnected / Connected)
  • PV Inverter Status (H:40193) – inverter availability and operation status flags
  • Continuous Power Output Capability (H:40134 with scale factor H:40135) – maximum continuous AC power output rating in watts
Additional capabilities

The Fronius Datamanager exposes many additional SunSpec registers not included in the current template. These include per-phase AC current and voltage (3-phase), AC frequency, apparent and reactive power, power factor, aggregate DC current and voltage, cabinet temperature, SunSpec event/fault flags, Fronius site-level power and energy totals across all connected inverters, and an active state code. On Hybrid inverters with battery storage, the Basic Storage Control Model (124) provides battery state of charge, charge/discharge rate control, and grid charging configuration. These can be added in a future template update.

On systems with multiple inverters on a Fronius Solar Net ring, use a minimum timeout of 10 seconds for Modbus queries. Fronius recommends sequential (not parallel) polling. A maximum of 6 inverters per Datamanager is recommended for acceptable response times.

Troubleshooting

No Modbus communication
  1. Verify Modbus TCP is enabled in the Fronius Datamanager web interface (Settings > Modbus > tcp)
  2. Confirm the SunSpec Model Type is set to int+SF (not float)
  3. Check the IP address – navigate to the Datamanager web interface to verify connectivity
  4. Ensure TapHome Core and the Fronius Datamanager are on the same network and subnet
  5. Check that no firewall is blocking port 502
Incorrect or zero readings
  • Wrong SunSpec Model Type: If set to float instead of int+SF, all register addresses shift and readings will be incorrect. The template initialization script sets this automatically, but if it failed, change it manually in the Datamanager web interface and re-import the template.
  • Multiple inverters: With more than one inverter on the Solar Net ring, verify the Slave ID mapping. Inverter #00 = Modbus ID 100, inverter #01 = ID 1.
  • Timeout issues: With multiple devices on the Solar Net, increase the polling timeout to at least 10 seconds. Queries must be sequential, not parallel.
String 2 shows invalid data

On inverters with only one DC input, String 2 registers return “not supported” values (0xFFFF for uint16). This is expected behavior – the String 2 device can be hidden in the TapHome interface.

Available devices

Fronius Symo Module
Service Attributes
Manufacturer
Device Model
Datamanager FW Version
Inverter SW Version
Serial Number
Phase ConfigurationInverter phase configuration — Single Phase, Split Phase, or Three Phase
ECP Connection StatusEnergy Communication Platform connection — Disconnected or Connected
PV Inverter StatusInverter availability and operation status flags
Continuous Power Output Capability

Fronius Symo

Service Attributes
Manufacturer
Modbusr(H, 40004, String, 32)
Device Model
ModbusR(H, 40020, String, 32)
Datamanager FW version
ModbusR(H, 40036, String, 16)
Inverter SW version
ModbusR(H, 40044, String, 16)
Serial number of the inverter
ModbusR(H, 40052, String, 32)
Phase
SWITCH(MODBUSR(H, 40069, Uint16), 111, "Single Phase",
112, "Split Phase",
113, "Three Phase",
"Unreachable")
ECP Connection Status
SWITCH(ModbusR(H, 40195, Uint16), 0, "Disconnected", 1, "Connected", "Unreachable")
PV Inverter Status
SWITCH(MODBUSR(H, 40193, Uint16), 
1, "Connected", 
2, "Available",
3, "Connected, Available",
7, "Connected, Available, Operating",
8, "Test",
"Not connected")
Continuous power output capability of the inverter [W]
modbusr(H, 40134, Uint16) * 
POWER(10, modbusr(H, 40135, int16))
Operating State Multi-value Switch Read-only

SunSpec inverter operating state — Off, Sleeping, Starting, MPPT, Throttled, Shutting Down, Fault, Standby

Register: H:40290 Int16 numeric
Values / States: Off · In Operation · Run-up Phase · Normal Operation · Power Reduction · Shutting Down · Fault · Standby

Operating State

Read switch state
MODBUSR(H, 40253+37, Int16)
PV Production Electricity Meter Read-only

AC production meter — current power output (kW) and cumulative lifetime energy (kWh)

Register: H:40101 (readtotalconsumption), H:40107 (readdemand) Float Unit: kWh / kW
Service Attributes
Frequency
Maximum AC Current Capability

PV Production

Read total consumption
MODBUSR(H, 40101, Float) / 1000
Read demand
MODBUSR(H, 40107, float) / 1000
Service Attributes
Frequency [Hz]
ROUND(ModbusR(H, 40093, Float, 2))
Maximum RMS AC current level capability [W]
ModbusR(H, 40143, UInt16) * POWER(10, ModbusR(H, 40144, Int16))
String 1 Variable Read-only

DC power from PV string 1 (W) — MPPT Extension Model

Register: H:40284 UInt16 * 10^(H:40267) Unit: W scale factor

String 1

Read
(MODBUSR(H, 40284, UInt16) * 
POWER(10, MODBUSR(H, 40267, Int16)))
String 2 Variable Read-only

DC power from PV string 2 (W) — MPPT Extension Model, not supported on single-input inverters

Register: H:40304 UInt16 * 10^(H:40267) Unit: W scale factor

String 2

Read
(MODBUSR(H, 40304, UInt16) * 
POWER(10, MODBUSR(H, 40267, Int16)))
Connection: Modbus TCP • Slave ID: $[SlaveId]
Possible improvements (20)
  • H:40072 AC Total Current — uint16, A, with A_SF scale factor
  • H:40077-40082 AC Voltages (phase-to-phase and phase-to-neutral) — uint16, V, with V_SF scale factor — 6 registers for 3-phase
  • H:40086 AC Frequency — uint16, Hz, with Hz_SF scale factor — template reads frequency via Float at H:40093 instead
  • H:40088 Apparent Power — int16, VA, with VA_SF scale factor
  • H:40090 Reactive Power — int16, VAr, with VAr_SF scale factor
  • H:40092 Power Factor — int16, %, with PF_SF scale factor
  • H:40097 DC Current — uint16, A, with DCA_SF scale factor
  • H:40099 DC Voltage — uint16, V, with DCV_SF scale factor
  • H:40103 Cabinet Temperature — int16, C, with Tmp_SF scale factor
  • H:40108 Operating State (Inverter Model) — enum16, standard SunSpec operating state at Inverter Model level (vs MPPT model used in template)
  • H:40110-40111 Event Flags — uint32, SunSpec event/fault flags (bits 0-31)
  • H:214 Active State Code — uint16, Fronius-specific active state code
  • H:500-501 Site Total Power — uint32, W, total power across all connected inverters
  • H:502-505 Site Energy Day — uint64, Wh, total energy for current day
  • H:510-513 Site Energy Total — uint64, Wh, total energy across all connected inverters
  • H:40311 Battery State of Charge — uint16, %, ChaState (SOC%). Was in old template revision but removed. Hybrid inverters only.
  • H:40309 Storage Control Mode — bitfield16, R/W — bit 0=CHARGE, bit 1=DISCHARGE. Hybrid inverters only.
  • H:40316 Max Discharge Rate — int16, R/W, % of WChaMax. Hybrid inverters only.
  • H:40317 Max Charge Rate — int16, R/W, % of WChaMax. Hybrid inverters only.
  • H:40321 Grid Charging — enum16, R/W, 0=PV only, 1=grid charging enabled. Hybrid inverters only.
Download Template

Sources