False information about new Cape Town data centre’s 4.4-billion litre water usage
Estimates of the water consumption used for cooling a new data centre set to be built in Cape Town are inaccurate, as the facility will not use water-based cooling at all.
The City of Cape Town recently approved the zoning application by US firm Equinix for two hyperscale data centres. Equinix is among the world’s largest data centre colocation firms.
It owns and operates 281 data centres across six continents, including some which are used by Internet and tech giants such as Amazon and Microsoft.
Two parties opposed to the development are the Housing Assembly and Foxglove, a UK-based tech justice non-profit organisation. They have retained Legal Resources Centre (LRC) to present their case.
Among their arguments against the facility is that it will consume substantial amounts of water for cooling, something a water-scarce city like Cape Town could hardly afford.
The LRC estimated that the data centre could consume 12.05 million litres of water per day or 4.4 billion litres (4,400 megalitres) per year.
The estimate was based on the data centre’s maximum electrical load of 174MW multiplied by the average 25.5 million litres consumed per megawatt (ℓ/MW) with conventional evaporative cooling.
There are several glaring issues with the estimate. Firstly, Equinix has publicly confirmed that the data centres will use dry-air-based cooling systems. These systems use virtually no water.
The downside of this technology is that it uses more electricity, which can increase water consumption at the power source, but not to the extent that it would match the consumption of water-based cooling.
Secondly, the 25.5 million litres per MW of electricity consumed in the calculation is based on the continuous IT load, not the electrical load.
The critical IT load of the Equinix facility will be 170MW. While its continuous IT load has not been confirmed, it will not exceed that figure.
It should be noted that Equinix has committed to avoiding evaporative cooling in water-stressed areas. As of 2023, only 34% of its sites used water-based cooling.
Estimated usage above all of Equinix’s existing data centres
At Equinix’s evaporatively cooled facilities, it drew 37% of its water from non-potable sources, which would not have been suitable for human consumption in any case.
Even if the Cape Town data centre was using evaporative cooling, it was highly unlikely it would consume anywhere near the estimates claimed by the LRC.
In Equinix’s latest sustainability report, published in 2024, it reported consuming 4.18 billion litres of water across its global data centre footprint.
The company has around 3GW of critical IT load in operation. The 170MW Cape Town facility would make up less than 6% of that.
Equinix’s portfolio-wide water usage effectiveness (WUE) is 0.95 litres per kilowatt-hour (ℓ/kWh). If applied to the IT load of the current data centre, it would consume 1.45 billion litres of water in a year.
Equinix’s sites that use water-intensive evaporative cooling have reported a WUE of 1.55ℓ/kWh. The 4.4 billion litres assumption of the LRC implies a WUE of 2.9ℓ/kWh.
For the data centre to consume 4.4 billion litres of water, it would need to use nearly twice the average of Equinix’s evaporatively cooled sites.
Equinix has yet to share precise details regarding the facility’s design, cooling type, critical IT versus utility power load, expected continuous IT load, and water sources.
This information is only required to consider the approval of Equinix’s Site Development Plan, which must still be presented to the city’s municipal planning tribunal.
Equinix Cape Town data centre water usage estimate vs reported usage
| Source | Annual water | Consumption |
|---|---|---|
| Legal Resource Centre’s calculation for 170MW | 4.4 billion litres | 2.9ℓ/kWh (implied/calculated) |
| Equinix reported water consumption in 2024 across 3,000MW of data centres | 4.18 billion litres | 0.95ℓ/kWh |
| Equinix water consumption at evaporative sites across global footprint | Unspecified | 1.55ℓ/kWh |
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