What happens to all the heat generated by Irish data centres?

Ireland's data centres generate substantial amounts of heat as a byproduct of their operations. In 2025, these centres consumed 23% of all electricity metered in the country, a significant increase from just 5% a decade earlier. The majority of this electricity is consumed by servers, with the remainder used for power conversion, backup systems, and cooling equipment.

Engineers evaluate the efficiency of these facilities using a ratio known as power usage effectiveness (PUE), which quantifies the extra electricity required beyond the computing process itself. While some modern facilities come close to a PUE of 1.0, indicating minimal overhead, older halls tend to expend more on overheads.

Currently, there is limited information available on the energy efficiency of individual data centres, making it challenging to determine which sites are operating optimally. However, this is set to change due to new EU regulations requiring larger data centres to report their energy use and environmental impact annually. While this reporting alone will not directly reduce electricity consumption, it is crucial for improving performance where data is available.

Ireland's climate presents an advantage for managing this heat. Throughout much of the year, the outside air is cool enough to facilitate heat removal without relying heavily on mechanical refrigeration. However, during warmer weather, more energy is needed to disperse the same amount of heat, which remains an area where data is insufficient to accurately assess the additional electricity consumption.

Despite this, there are several straightforward measures that can reduce energy use without compromising reliability. These include adjusting the control of cooling equipment, allowing the chilled water to run at slightly higher temperatures, and replacing aging chillers. None of these require advanced technology; they are decisions that can be implemented immediately.

Looking ahead, the industry is shifting towards liquid cooling, a method that replaces air with a liquid to remove heat from servers. This change is particularly relevant for AI training racks, which consume significantly more power than conventional racks. Liquid cooling produces warm water, which can be repurposed to heat buildings when utilized with a heat pump.

At a temperature of around 70°C, this warm water is sufficient for heating purposes. In Tallaght, Ireland, an existing example of this approach is the Tallaght District Heating Scheme, which redistributes waste heat from an Amazon data centre to supply County Hall, TU Dublin's Tallaght campus, and 133 apartments. This system has already saved over 1,400 tonnes of carbon dioxide in 2025 and there are plans to expand it to serve thousands of homes.

However, despite the existence of this scheme, only one such system currently exists in Ireland. This disparity is attributable to several factors, including geographical location, cost considerations, and the fact that waste heat is often of little value to the operators themselves. To address this, EU rules already mandate that data centres exceeding one megawatt must seek to reuse their heat where feasible.

Furthermore, the European Commission has proposed a common rating scheme for data centres exceeding 500 kW, taking into account energy and water use, waste-heat reuse, and their contribution to the broader energy system. These labels are anticipated to be introduced in 2027, and a Heat Bill aimed at regulating district heating is also in the pipeline.

In summary, while Ireland's data centres generate significant heat, there is a notable lack of data and systematic efforts to manage and utilize this heat effectively. As the industry moves towards more efficient cooling methods and the implementation of new regulatory measures, there is potential for a transformative shift in how data centers contribute to Ireland's energy landscape.