An innovative study on the efficiency of evaporative coolers has been undertaken by the Australian Institute of Refrigeration Air Conditioning and Heating (AIRAH), supported by the Smart Water Fund, Department of Sustainability and Environment (DSE) and the Plumbing Industry Commission (PIC). Up until now, there has been no understanding or consideration about water efficiency in the installed stock of evaporative coolers in Victoria. Evaporative cooler operation is based on very simple physics and the equipment life can be up to 20 years.

In 2009, AIRAH prepared a report "Industry Perspective of Water Inefficiencies in Evaporative Coolers" for DSE, which considered the way installed evaporative coolers are used in Victoria. The report was based on discussion and input from a broad range of stakeholders including technical and non technical experts from within regulators and water retailers.

AIRAH's research indicated that approximately 550,000 residential evaporative coolers have been installed in Victoria alone, with an estimated overall water consumption associated with their use to be about 15 gigalitres (GL) annually. Estimates also suggested water excess (waste) is in the realm of 20%, or 3 GL/year. These losses were generally attributed to controlled losses due to improperly commissioned water management settings, poor levels of maintenance and service and inappropriate operation by consumers, many of whom had bought mass-builder built homes and had not been given instructions for the appropriate use of evaporative coolers. The report recommended that field trials be undertaken to accurately calculate the water savings that could achieved in the commercial setting and with a cross-section of domestic users.

In 2010, AIRAH applied to the Smart Water Fund to undertake the recommended field trials in Victoria for residential and non-residential evaporative cooling systems. This included on-site visits to 50 residential and 50 non-residential evaporative coolers across metropolitan and regional areas. The visits looked at each unit's water consumption to determine if water was being wasted.

Evaporative coolers use water in two ways – through the process of evaporating water to provide cool air, and secondly to reduce mineral build up through a bleed off or dump process. The dump process is where excess water is discarded all at once, whereas a bleed system releases smaller amounts over time.

In the residential sector, the research concluded that evaporation rates for modern evaporative units approximates between 60 and 100 litres per hour (L/hour), depending on typical seasonal variations in Victorian ambient air conditions and model characteristics. The average purge rate encountered in this study was approximately 20 L/hour, amounting to approximately 25% of evaporation rates with current equipment settings. In order to improve water efficiency, it was recommended that by operating evaporative units without bleed, but dumping the full system volume once per 24 operating hours during the summer months, non-evaporative water savings of around 95% could be achieved, equating to around 2.5 GL/year (17% of estimated overall water consumption associated with evaporative coolers in Victoria). While newer systems can be set to operate in this fashion, older systems would need to be modified or replaced.

In the non-residential sector, it was found that many evaporative coolers operate inefficiently and that there is potential to save 1.8 GL of water annually if all non-residential evaporative coolers in Victoria were operated according to best practice.

A range of resources have been developed as a consequence of the field trials, including:

• "DA29 – Evaporative Air Cooling Systems" – a detailed technical guide aimed at engineers. This manual covers the full life cycle of evaporative coolers from design, installation, commissioning, operation, maintenance to recommissioning.
• "Non-Residential Evaporative Air Cooling Systems – Water Efficiency and Conservation Best Practice Guidelines" – this guide is aimed at non-residential end users, and can be downloaded from www.airah.org.au.
• "Residential Evaporative Air Cooling Systems – Water Efficiency and Conservation Best Practice Guidelines" – this guide is aimed at residential end users, and can downloaded from www.airah.org.au.

AIRAH has also negotiated funding with PIC to develop training for plumbers focusing on water conservation measures for evaporative coolers. The training will focus on the modification process for evaporative coolers to improve their water efficiency.

If you would like further information on the project, or a copy of the final report, please contact Dr. Sarah Gray, Knowledge Transfer Manager on This e-mail address is being protected from spambots. You need JavaScript enabled to view it or (03) 9552 3171.