NoVA Data Centers and UHI/climo effects

[LordBaltimore]

Surprised I haven't seen much if any mention of this lurking around the forums. As everyone knows NoVa and specifically Ashburn, VA is *the* hub of the AI data center boom going on right now. And as everyone also knows, data centers use a ton of water and electricity - most of which ultimately ends up in the atmosphere as waste heat and water vapor. Thinking about this from an urban heat island perspective, you could chalk it up as typical development in an area that's been sprawling for decades, except you'd be way off on scale. These things are unprecedented in terms of energy and water throughput density, they compare absolutely none to any other type of development we've seen before ever and I highly suspect if people looked closely we'd already see some unique effects on regional climate that will continue to grow as more of these things come online in a very concentrated area. 

How do data centers compare to other sources of UHI?

Scale - around 6 GW of capacity used for existing data centers in Loudon county alone, future plans might require upwards of 20. Roughly 2 billion gallons water consumption. Total VA build out, most of which is in NoVA would consume 66 to 100 TWH per year, which is comparable to the state of Tennessee. 

This isn't normal sprawl. It is the energy usage of entire states, concentrated into waste heat and moisture in a few square miles. It dwarfs the energy consumption of DC proper. The water usage otoh is about 5% of what DC consumes - not off the scale - but consider how it's used. 

Interaction w/ Environment - New build data centers tend to be built using closed-loop cooling systems, featuring roof-top cooling towers that use airflow + evaporation to chill an internally circulated coolant. I can't find an actual source, but chat GPT suggests that roughly 80% of the waste heat handled by these systems is offset by latent cooling, with about 20% remaining in sensible heat to the atmosphere. All of that water is for the most part being output to the atmosphere rather than being flushed to the bay like most urban water supply - so that 5% figure is actually quite significant. And since these cooling towers are quite low/not that hot, unlike the direct cooling towers on power plants, the moisture output is all going into the PBL rather than the free atmosphere. Long story short, gigawatts and gigawatts of energy is being used to humidify the lower atmosphere in NoVA. 

It's important to note that this waste heat and humidity is being output in a suburban area, so it will express itself in unfamiliar ways compared to traditional urban UHI. From most studies I've seen, daytime urban UHI is primarily SW albedo + transpiration effects, whereas nightime UHI is attributed to radiative inefficiency (urban canyon + higher heat capacity of surfaces) and waste heat from buildings and vehicles. The night-time effects notoriously combine in various ways, and so for waste heat in a suburban areas you may not see the dramatic increase in over-night minimums that are usually the hallmark of UHI, since there aren't the same kinds of surfaces to trap spatially and temporally varying fluxes of waste heat and dispense them out evenly over the AM hours, and the fluxes from data centers are not as uniform in the first place as cars and buildings that ring every block of a city. 

Questions

Do observations so far indicate anything odd around NoVA? Temperature wise, but also dewpoints

How widespread would any effects be? Would it be hyper-local within NoVA or would we get significant downstream transport? 

If the waste heat and moisture output of data centers is significant, will it express itself in changes to regional convective season climo? This seems reasonable since PBL moisture distribution is a huge factor

I plan to dive through the data at some point and post updates, but right now I thought I'd get some input to make sure it's not crazy

 

Here are some articles on NoVA data centers and their electricity/water usage:

https://www.businessinsider.com/virginia-data-center-construction-boom-amazon-2025-10

https://www.visualcapitalist.com/map-network-powering-us-data-centers/

https://www.itbrew.com/stories/2024/08/26/northern-virginia-s-data-center-alley-is-thirstier-than-ever