ista's smart cooling meters deliver precise and reliable measurement.

Cooling insights that drive efficiency.

In an era of rising energy costs and growing demands for sustainability, accurate metering is more important than ever. ista’s cooling meters are designed to measure the precise amount of energy transferred through chilled water systems. Whether in residential buildings or large commercial setups, our meters provide the basis for fair billing, energy transparency, and efficient facility management. Thanks to their robust, MID-compliant design and advanced communication options, they are a future-proof, scalable solution. 

The technology behind precise cooling measurement.

A cooling meter, also known as a BTU (British Thermal Unit) meter, is used to measure the thermal energy consumed in chilled water systems. It combines three key components: a flow sensor, two temperature sensors, and a microprocessor-based energy calculator. The flow sensor is installed in the return line, while the temperature sensors are placed in the supply and return lines. The meter calculates the transferred energy by comparing the temperature difference with the volume of water that has flowed through the system.

Ultrasonic cooling meters measure flow using ultrasonic signals rather than mechanical parts. This method is free from wear and tear, silent, and highly precise — even at low flow rates or in systems with poor water quality. Since there are no moving components, ultrasonic meters offer long-term stability, minimal maintenance and excellent durability, making them the preferred choice for modern energy monitoring.

At ista, we offer cooling meters  for every building type and installation scenario. Our devices are developed with German engineering expertise, combining technical precision with a robust, field-tested design. Whether you are equipping a residential high-rise or a large-scale commercial property, our meters provide reliable performance and clear data for accurate energy billing.

Precision and accuracy in one device: ista's ultego III

The ultego III smart plus and ultego III perfect are part of ista’s latest generation of cooling meters — developed for flexible use across a wide range of building types and system sizes. Designed for use in systems with water as the cooling medium, the compact ultego III smart plus integrates a flow sensor, two external temperature sensors, and a high-precision energy calculator. If needed, the calculator can be mounted separately, and sensor cable lengths can be specified to suit installation requirements.

With flow rates ranging from 0.6 to 60 m³/h, the meter is suitable for applications ranging from individual transfer stations to large multi-unit buildings. Its robust, all-metal DuraSurface™ housing and flexible installation options (horizontal, vertical or even upside down) ensure stable performance in tight spaces and areas with high humidity. Integrated communication modules — including M-Bus, wireless M-Bus, and pulse output — enable seamless integration into remote reading and building automation systems. Compliant with the European Measuring Instruments Directive (MID), the ultego III smart plus provides a durable, future-proof metering solution for scalable energy monitoring.