Picture a flat in Espoo, just west of Helsinki, on a dark January evening. It's minus fifteen outside. The radiators are warm, and a share of that heat started out as the waste from servers in a Microsoft data hall a few kilometres away, lifted to district heating temperature by some of the largest heat pumps in Europe.
The household doesn't know or care. But that one radiator holds the whole argument about data centres and climate.
To some people, data centres are the reason climate targets are slipping. To others, they're the biggest private source of money for the energy transition. The interesting answer is that both are true at the same time, and the people building them are caught in the middle.
The case for the prosecution
Start with the companies' own numbers, because they don't hide them.
Microsoft's 2026 sustainability report shows total emissions up about 25% in a single year, to roughly 20 million tonnes. The company puts it down to data centre expansion and to a deliberate change in how it buys clean energy (it stopped counting cheaper, "non-additional" renewable certificates). Amazon reported a 16% rise in 2025, driven largely by data centres. Google's electricity use rose 37% and its total emissions grew too, mostly from manufacturing chips and servers, and its own report says its climate goals are "getting harder".
The wider picture is similar. The IEA expects global data centre electricity use to more than double, from about 415TWh in 2024 to around 945TWh by 2030. It also expects gas to supply a meaningful share of that growth, especially in the US.
And gas is already on site. With grid connections slow, on-site generation has gone mainstream, and turbine makers are sold out years ahead. GE Vernova's gas backlog and reservations reached 116GW this summer, and it says around a fifth of that is explicitly for data centres.
The case for the defence
Now look at who is paying for new clean power.
According to BloombergNEF, Amazon, Meta, Google and Microsoft signed 49% of all corporate clean power deals in the world in 2025. Meta and Amazon each contracted more than 10GW. Google signed more than 12GW of new clean energy in a single year. These contracts are what get wind farms, solar parks and storage projects financed.
Then there's nuclear, which a few years ago almost nobody in tech would have touched:
- Microsoft and Constellation are restarting the undamaged reactor at Three Mile Island, now called the Crane Clean Energy Center. That's 835MW, under a 20-year agreement, with power targeted for 2027.
- Google and Kairos Power have a deal for up to 500MW of small modular reactors by 2035. The first, Hermes 2 in Tennessee, is due in 2030.
- Amazon and X-energy are aiming for more than 5GW of SMRs by 2039, starting with a 320MW plant in Washington State.
- Meta signed agreements in January for up to 6.6GW of new and existing nuclear capacity.
And back in Espoo, the Fortum heat pump plants are built and running. Once Microsoft's halls are online, their waste heat is expected to cover around 40% of district heating demand for about 250,000 people, replacing heat that used to come from coal.
So which is it?
Both, and that's what matters for contractors.
Data centres are adding demand faster than clean supply can keep up, and in the short term some of that gap is being filled with gas. They are also signing the long-term contracts that are paying for the next generation of clean power, nuclear included. The IEA's own conclusion is careful: AI can help cut emissions, but "it is not a silver bullet".
There is one thing the two sides agree on, though. A data centre is no longer just a building with power going into it. It's turning into an energy project, with generation, storage, heat export and in some cases a reactor in the contract. Regulators are pushing the same way: in Germany, new data centres that started operating from July this year have to reuse 10% of their energy, rising to 20% by 2028.
That changes who you need on the job.
The energy side is becoming its own labour market
Five skill sets that used to sit outside data centre projects are now inside them:
HV and generation. Projects with on-site gas turbines or engines need people who have built power plants, not just switch rooms. Many tenants still resist gas, which means the alternatives (fuel cells, hybrid systems, biofuels) bring their own learning curve.
Battery storage. BESS is moving from a grid-services add-on to part of the data centre's design. Microsoft has replaced diesel generators with batteries at a site in Sweden, and Google has replaced diesel generators with a grid-scale battery at its Belgian campus. Commissioning BESS is a different discipline from commissioning UPS.
Heat recovery and district heating. Large heat pumps, heat exchangers and interfaces with a utility's network, under a contract with a third party who has their own programme. These are people who have more often worked for energy companies than for M&E contractors.
Nuclear-adjacent work. SMRs won't sit inside data centre perimeters in this decade. But the campuses connected to them will need people who understand nuclear-grade quality assurance, documentation and safety culture. That pool is tiny, and the restart and new-build programmes are drawing on the same people.
Refrigerants. The move to lower-GWP, mildly flammable A2L refrigerants means chiller and cooling teams need retraining. The EU F-gas rules are tightening again in 2027 for larger chillers, and certification now has to cover A2L handling.
None of these people come from the traditional data centre pool, and every one of them is also being hired by utilities, renewables developers and the power sector. The energy transition and the data centre boom are competing for the same people.
What this means on site
- Map the energy scope early. Ask at bid stage whether the job includes generation, BESS, heat export or a utility interface. Each needs a named lead, and none of them can be added in the week before mobilisation.
- Hire across the fence. The best heat recovery engineer for your next job probably works for a utility. The best BESS commissioning lead may be in renewables. Look beyond data centre CVs, and pair those people with your own data centre team.
- Get ahead of A2L. Find out how many of your cooling engineers and service partners are certified for A2L handling now, before a client's specification or a regulator asks.
Three numbers worth knowing
49%: the share of global corporate clean power deals signed by Amazon, Meta, Google and Microsoft in 2025, according to BloombergNEF.
25%: the year-on-year rise in Microsoft's reported emissions in its 2026 sustainability report, driven by data centre expansion and a change in how it buys clean energy.
10%: the share of energy that new data centres in Germany must reuse from July 2026, rising to 20% by 2028.
So, enemy or funder?
Both, for now. The industry is adding emissions in the short term and paying for a lot of the long-term fix.
For the people who build data centres, the label matters less than the result: the scope of the job now runs from the substation to the heat network, and possibly to a reactor. The contractors who staff for that will win the next round of work.
One question back to you: has energy scope (generation, BESS, heat recovery) turned up on one of your projects yet, and who did you get to deliver it? Reply and tell me. I read every answer.
Alex The DC Build Network