What are the differences between BMS software and EMS software?

A BMS and an EMS are two distinct pieces of software that do not meet the same need. A Building Management System (BMS) controls and monitors technical equipment. An Energy Management System (EMS) analyses consumption to improve energy performance. On the same site, the two tools complement each other.

BMS software controls a building

A BMS controls the technical installations of a building or site in real time.

What a BMS supervises

Heating, ventilation, air conditioning, lighting and hot water production report to a single supervision station. Some BMS also integrate technical alarms and access control.

How it works

Controllers and sensors communicate with the supervisor through protocols such as BACnet, Modbus, KNX or LonWorks. The software acts directly on the equipment. It sets temperature setpoints, schedules time slots, switches equipment on and off and reports faults.

When an air handling unit fails on a Saturday, the on-call technician receives the alarm and restarts the equipment remotely.

BMS users are the operations and maintenance teams.

BACS decree

The BACS decree makes a building automation and control system mandatory in commercial buildings whose heating or air conditioning exceeds 70 kW. The obligation has applied since 1 January 2025 above 290 kW. For existing buildings between 70 and 290 kW, decree no. 2025-1343 of 26 December 2025 postponed the deadline to 1 January 2030.

Source: Decree no. 2025-1343 of 26 December 2025

EMS software tracks energy consumption

An EMS collects and analyses a site's energy consumption to improve its performance. It does not control any equipment.

The data collected

The EMS aggregates metering and sub-metering data for electricity and fluids (gas, steam, compressed air, fuel oil and water). It can cover several sites. It works in read-only mode, at time steps ranging from a few minutes to an hour or a day.

The analyses produced

From these measurements, the software calculates energy performance indicators (EnPIs) and provides dashboards for carrying out analyses. It detects drifts, measures the savings achieved and produces reports.

Users are energy managers, senior management and HSE managers.

A tool serving ISO 50001

The ISO 50001 standard requires an energy management system to demonstrate continual improvement in its energy performance. This demonstration relies on EnPIs compared with an energy baseline. The EMS provides these measurements.

Synergies between BMS and EMS

The EMS identifies savings opportunities. The BMS acts on the equipment. The two are complementary.

The BMS provides data to the EMS

Some BMS information can feed the EMS, such as room temperatures. The EMS cross-references it with energy consumption data.

The EMS guides BMS settings

The savings opportunities identified by the EMS can be implemented in practice through the BMS.

The EMS shows that a workshop's heating runs on Sundays while production is stopped. Maintenance reprograms the time slots in the BMS. The EMS then compares consumption over the following weeks and quantifies the actual savings.

Wattseeker is EMS software

Wattseeker is the energy management software (EMS) designed and developed in France by Qualisteo.

This software aggregates electricity, gas, water, steam, compressed air and fuel oil consumption, as well as production data. Consumption is displayed by zone, by use or by piece of equipment, in real time.

Alarms flag drifts and consumption peaks.

Wattseeker is interoperable. The software works with Qualisteo's Lynx connected sub-meters and with other measurement technologies made by other manufacturers.