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Legionella safe & energy efficient domestic hot water with limited water volume

Optimization of energy use is central for sustainable development. A contributing factor for optimization is the temperature of the domestic hot water. It is a compromise between energy use and microbial safety. The project studies a limited water volume solution that allows the water temperature to be reduced without increasing Legionella risk.

Aim and goal

This project aims at evaluating how a limited domestic hot water (DHW) volume at reduced temperature will affect the growth of Legionella and how such a system could be implemented in real buildings.


One important aspect in sustainable building is to optimize energy consumption, with DHW temperature being one essential factor. The optimal DHW temperature is often a balance between energy demands and microbial safety, in particular the risk of Legionella spp. at temperatures below 50 °C. Methods to remove Legionella used today has been shown to last for a short time and give rise to e.g. problems with leakage due to damage on the DHW installations. There is therefore a need to investigate novel approaches to solve this problem.


In new building constructions and renewal projects it is important to design the DHW system correct to minimize energy consumption and lower the risk of Legionella. One such approach would be to use a small volume of DHW, e.g. 3 L, and to heat the water instantaneously when needed. This approach has been tested in Germany and Denmark, but further evaluations are needed under Swedish conditions. There is also a need to study the Legionella biofilm formation under controlled conditions in such a system to be able to assess the risks in a long-term perspective.


The investigated system could potentially provide a stronger Legionella protection, and simultaneously allow a reduction of the DHW temperature with substantial reduction in the energy consumption.


Project name

Legionella safe domestic hot water



RISE role in project

Project manager

Project start


2,5 år


Lund University, 19 partners representing technology suppliers, energy companies, consultants


Formas, Project information in Formas project database

The UN sustainable development goals

3. Good health and well-being
6. Clean water and sanitation
9. Industry, innovation and infrastructure
11. Sustainable cities and communities

Project members

Charlotta Löfström

Contact person

Charlotta Löfström


+46 10 516 67 30

Read more about Charlotta