Modbus – The Industry's Most Used Communication Protocol

When different technical systems in a building need to communicate with each other, a common language is required. One of the most widely used communication protocols in building automation, energy monitoring, and industry is Modbus.

Although Modbus was developed back in 1979, it is still used in millions of installations worldwide. The reason is simple: the protocol is open, robust, and easy to implement.

In this article, we will explain what Modbus is, how it works, and why it still plays an important role in modern buildings.

‍

What is Modbus?

Modbus is a communication protocol used to transfer data between different devices. The protocol was developed by Schneider Electric (formerly Modicon) for communication between PLC systems and other industrial equipment.

Today, Modbus is used to connect, for example:

• Energy meters
• Electricity meters
• Water meters
• Heat meters
• Ventilation units
• Heat pumps
• Solar power systems
• Battery storage systems
• Building automation systems (BMS/BAS)

Modbus is an open standard, which means that products from different manufacturers can communicate with each other as long as they follow the same specification.

‍

How does Modbus work?

Modbus is based on a simple principle where one device asks questions and another provides answers.

Traditionally, there are two roles:

Master (Client)

The Master device initiates communication and sends requests.

Slave (Server)

The Slave device responds to requests from the Master device.

Example:

1. A gateway sends a request to an electricity meter.
2. The electricity meter reads its current energy value.
3. The electricity meter sends back the value.
4. The gateway stores or forwards the information to a higher-level system.

The Master device always controls the communication.

‍

Modbus Registers – where information is stored

In Modbus, data is stored in so-called registers.

Each register has a unique address where different types of information are stored.

Example:

Register Information40001Voltage40002Current40003Power40004Energy Consumption

When a gateway or a supervisory system wants to read a value, it sends a request to read a specific register.

The response then contains the current value.

‍

Modbus RTU and Modbus TCP

There are two main variants of Modbus.

‍

Modbus RTU

Modbus RTU uses serial communication, usually via RS485.

Advantages:

• Robust and reliable
• Long communication distances
• Low cost
• Common in energy meters and building automation

Communication takes place via a two-wire cable where multiple devices can be connected to the same bus.

Modbus TCP

Modbus TCP uses Ethernet and IP networks.

Advantages:

• Higher transmission speed
• Easy integration with IT systems
• Can use existing network
• Easy Remote Access

Modbus TCP is becoming increasingly common in modern buildings where many systems are already connected to local networks.

‍

Advantages of Modbus

Modbus remains one of the world's most widely used protocols due to several strengths:

Open Standard

No license is required to implement Modbus.

Broad Support

Thousands of products from various manufacturers support Modbus.

Easy Integration

Relatively easy to connect different systems and vendors.

Stable Technology

After more than 40 years on the market, Modbus is well-proven and documented.

Scalable

Can be used in everything from small installations to large property portfolios.

‍

Limitations of Modbus

Despite its advantages, there are certain limitations.

No Automatic Device Identification

Each device typically needs to be configured manually.

Limited Data Structure

Modbus is primarily designed for numerical values and lacks modern features for more complex data management.

No Built-in Encryption

The standard protocol includes no security features, meaning secure communication often needs to be handled externally.

[SEG 5]
‍

Modbus in Modern Buildings

In today's buildings, Modbus is often used to collect data from technical installations and energy systems.

Examples of Use Cases:

Energy Metering

• IMD (Individual Metering and Billing)
• Solar Power Systems
• Battery Storage
• Ventilation and HVAC
• Heat Pumps
• EV Charging Infrastructure
• Building Automation Systems
• By collecting data from various systems, property owners can gain better control over energy consumption, operation, and maintenance.
  
  [SEG 18]
  ‍
  

Mivo Connect and Modbus

MIVO Connect has built-in support for both Modbus RTU and Modbus TCP. This enables data collection from a wide range of devices and manufacturers via a common platform.

Data can then be forwarded to systems such as:

• Energy management systems (EMS)
• Building automation systems (BMS/BAS)
• IMD systems
• Analysis and reporting platforms
• Cloud-based IoT solutions

By combining Modbus with open communication interfaces, a flexible and future-proof solution is created, allowing property owners to avoid vendor lock-in.

‍

Summary

Modbus is one of the world's most established communication protocols for energy and building automation. Thanks to its simplicity, open standard, and broad compatibility, it is still widely used to connect meters, sensors, and control systems.

For property owners, Modbus offers an opportunity to collect valuable operational and energy data from many different types of equipment and create more efficient, data-driven, and sustainable property management.

‍