E3/DC e3dc (grid)
The E3/DC e3dc (grid) is a single-register Modbus TCP meter template targeting the grid connection point of E3/DC home power stations (S10 product family). It reads the instantaneous grid power from holding register 40073 as a signed 32-bit integer: positive values indicate power drawn from the grid, negative values indicate export to the grid. The ModbusCloud Gateway connects to the E3/DC unit over the local Ethernet network on port 502. This template gives installers and energy managers a live view of grid exchange in the ModbusCloud portal without any additional hardware.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 1, read only
- Brand
- E3/DC
- Last updated
Registers (1)
1 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read |
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Use cases
- Monitor real-time grid import and export to verify that the E3/DC system is operating within expected power limits.
- Alert on sustained grid import above a threshold to detect when battery storage is no longer covering household load.
- Track grid export values over time to confirm that feed-in limits imposed by the grid operator are not exceeded.
- Compare grid power readings against expected PV production to identify unexpected consumption patterns or metering faults.
- Report daily grid exchange totals to building owners as part of a monthly energy performance review.
Installation
Enable Modbus TCP on the E3/DC unit: navigate to Main Menu, then Functions (or Smart Functions > Smart Home depending on firmware), select Modbus, switch Modbus on, then enable Modbus TCP and confirm the protocol is set to E3/DC or E3/DC Simple-Mode.
Connect the ModbusCloud Gateway to the same local Ethernet network as the E3/DC unit and confirm both devices can reach each other; the E3/DC listens on TCP port 502 by default.
In the ModbusCloud portal, add the Gateway, import the E3/DC e3dc (grid) template, and set the unit ID to 1 (the E3/DC default) and the port to 502 unless you have changed these in the device menu.
Verify the connection by checking the live reading for the power register in your portal dashboard; a value near zero or matching your current grid situation confirms a successful read.
Things to watch for
The power register always reads zero or a fixed wrong value. What is wrong?
E3/DC stores its 32-bit power values in swapped word order (low word first, high word second), sometimes called int32s or int32sw. If your client reads the two 16-bit registers in standard big-endian order, the result will be incorrect. Confirm that your Modbus client or the ModbusCloud Gateway decodes the register as a swapped int32.
The gateway connects but the portal shows no data. What should I check?
First confirm that Modbus TCP is actually switched on in the E3/DC menu, not just Modbus. The feature requires two separate toggles: Modbus enabled, then Modbus TCP enabled. Also verify the unit ID matches (default is 1) and that no local firewall or VLAN is blocking port 502 between the Gateway and the E3/DC device.
Register values look correct at first but then freeze or disconnect intermittently.
E3/DC devices do not always re-establish a dropped TCP connection automatically. If the ModbusCloud Gateway loses the session, it must reconnect. Ensure the polling interval is not set too short, as very frequent queries can stress the E3/DC Modbus stack. A poll interval of 10 seconds or longer is generally stable.
The sign of the power value seems inverted. Is positive import or export?
Per the E3/DC Modbus specification, a positive value at register 40073 means the system is drawing power from the grid (import), and a negative value means the system is feeding power into the grid (export). If your dashboard shows the opposite of what you expect, check that no scale factor of -1 has been applied in the template or your portal configuration.
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