Viessmann Climate Solutions and NHW agree on efficiency guarantee for heat pump systems in residential buildings
By signing a cooperation agreement between Viessmann Climate Solutions and MET, an NHW subsidiary, both partners are sending a clear signal in favor of economical, predictable, and practical solutions in the field of heat pumps for rental housing. The aim is to gradually replace or supplement heating systems in existing rental buildings with renewable energy systems.
Kassel/Allendorf (Eder), March 11, 2026 – Viessmann Climate Solutions and the Nassauische Heimstätte | Wohnstadt (NHW) group of companies are intensifying their cooperation in the transformation of heat supply in Hessian housing stock. With the conclusion of a cooperation agreement between Viessmann Climate Solutions and MET, an NHW affiliate, both partners are sending a clear signal for economical, predictable, and practical solutions in the field of heat pumps in rental housing construction.
NHW is one of Germany's largest residential property companies. Its subsidiary Medien-Energie-Technik GmbH (MET) specializes in media infrastructure, energy supply, and metering services. Viessmann Climate Solutions is part of Carrier Global Corporation (NYSE: CARR), global leader in intelligent climate and energy solutions.
The aim of the partnership is to gradually replace existing heating systems in rental buildings—most of them fossil fuel-powered – with renewable systems or make sensible substitutions. The focus is not only on reducing CO₂ emissions, but also on ensuring the long-term efficiency, operational reliability, and cost-effectiveness of the systems.
Reliable efficiency as the basis for economical heat pump projects
The core of the cooperation agreement is a binding efficiency guarantee based on the annual performance factor (APF) of the installed heat pump systems. This key figure describes the ratio of the amount of heat provided to the electrical energy used and is decisive for the economic evaluation during ongoing operation.
Viessmann Climate Solutions and MET are committed to planning, designing, and operating systems in such a way that a defined minimum efficiency is achieved. This gives housing companies and operators a high level of investment and operational security – an increasingly important factor in view of rising demands for climate protection, energy efficiency, and cost stability.
“The energy transition in existing buildings is not determined solely by the technology installed, but also by actual operational efficiency,” says Thomas Alt, Head of Commercial Business at Viessmann Climate Solutions. “With the efficiency guarantee, we and MET are taking responsibility for the entire life cycle of the systems – from planning to ongoing operation. This is an important step toward making heat pumps a viable and economical option for commercial buildings as well.”
Focus on heat pump solutions for existing buildings
While heat pumps are already established in new buildings, the cooperation focuses in particular on their efficient integration into existing buildings. The aim is to use heat pump systems in such a way that they enable economical and reliable operation without the need for comprehensive, cost-intensive full modernization.
“For us as a heating contractor, the focus is on ensuring that heat pump systems in existing buildings not only function technically, but can also be operated economically and reliably for many years,” says Michael Mahlich, Managing Director of Medien-Energie-Technik GmbH. “The efficiency guarantee provides a solid foundation for this. It gives us and the housing industry the necessary security to consistently push ahead with the switch to renewable heat generation, even in complex existing buildings.”
To this end, practical experience gained from real-life projects is systematically incorporated into planning and operations. The partners are thus pursuing an approach that takes equal account of the requirements of the housing industry, the technical conditions of existing buildings, and the expectations of tenants.
Nassauische Heimstätte Group | Wohnstadt (NHW)
NHW, based in Frankfurt am Main and Kassel, has been offering comprehensive services in the areas of housing, construction, and development for over 100 years. With around 61,000 rental apartments at 112 locations in Hesse, it is one of Germany's leading housing companies. Under the ProjektStadt brand, it carries out sustainable urban development projects. It is a founding member of the Wohnen.2050 initiative, which aims to make climate protection in the housing industry more effective. Its subsidiary MET offers high-performance multimedia services, supplies affordable, environmentally friendly energy, and provides technical and real estate services related to housing. www.nhw.de/
About Viessmann Climate Solutions
Founded in 1917 as a heating technology manufacturer, today Viessmann Climate Solutions is a leading global provider of sustainable climate (heating, cooling, water and air quality) and renewable energy solutions. The integrated Viessmann Climate Solutions portfolio seamlessly connects products and systems via digital platforms and services, creating an individualized feel-good climate for users. Viessmann Climate Solutions is part of Carrier Global Corporation, global leader in intelligent climate and energy solutions. For more information, visit www.viessmann-climatesolutions.com
