Deep water cooling involves using naturally cold water as a heat sink in a heat exchange system, eliminating the need for conventional air conditioning. The cold water is drawn from near the bottom or below the thermocline of a nearby water body. In this study Canadian deep water cooling systems in Halifax, Nova Scotia and Toronto, Ontario were documented. The expected economic and environmental benefits were realized, but barriers to large-scale adoption of the technology were apparent. This technology requires that a client with a large cooling need is near a deep, cold body of water, and payback times vary depending on the site. The public-private partnership approach proved to be beneficial in these two examples, and the Toronto approach in which many buildings are serviced at once by combining municipal pumping capacity can deliver cost savings on a shorter time span. Deep water cooling represents a successful example of a niche accumulation process and an example of electricity demand displacement. Many other locations in which heavy air conditioning users are located next to deep, cold water bodies could use this technology; several such sites exist in Canadian urban areas. (C) 2008 Elsevier Ltd. All rights reserved.