Explainer: Green IT & sustainable data centers — what it is, why it matters, and how to evaluate options

Data centers consumed approximately 460 TWh of electricity globally in 2025, representing roughly 1.8% of total worldwide electricity demand. The International Energy Agency projects this figure could reach 800 TWh by 2030, driven primarily by artificial intelligence workloads, cloud computing expansion, and the proliferation of edge infrastructure. For sustainability professionals, Green IT and sustainable data centers have moved from a niche concern to a strategic imperative that directly affects corporate carbon footprints, energy costs, regulatory compliance, and stakeholder expectations.

Why It Matters

The environmental footprint of digital infrastructure is growing at a rate that threatens to undermine corporate emissions reduction targets. A single hyperscale data center can consume as much electricity as 80,000 European households, and water consumption for cooling can exceed 5 million liters per day during peak summer months. Microsoft disclosed that its global water consumption increased 34% between 2021 and 2023, largely attributable to data center expansion to support AI workloads. Google reported a 17% increase in greenhouse gas emissions in 2024, with data center energy demand identified as the primary driver.

The regulatory landscape is tightening rapidly, particularly in the European Union. The EU Energy Efficiency Directive (EED), revised in 2023, requires data centers with 500 kW or more of installed IT capacity to report energy performance metrics beginning in May 2024. The European Commission's Delegated Regulation on data center sustainability indicators mandates disclosure of Power Usage Effectiveness (PUE), Water Usage Effectiveness (WUE), renewable energy usage, waste heat reuse, and cooling system efficiency. The Corporate Sustainability Reporting Directive (CSRD) further requires companies to disclose the environmental impact of their digital infrastructure within broader sustainability reporting.

Beyond regulation, corporate procurement decisions increasingly factor in the sustainability performance of IT infrastructure providers. A 2025 survey by Uptime Institute found that 67% of enterprise IT decision-makers now include sustainability criteria in data center procurement evaluations, up from 38% in 2022. Cloud customers are demanding carbon-free energy matching, water stewardship commitments, and circular economy practices from their providers, creating competitive pressure that is reshaping the industry.

Key Concepts

Power Usage Effectiveness (PUE) measures the ratio of total facility energy to IT equipment energy. A PUE of 1.0 would mean all energy goes directly to computing, while a PUE of 2.0 means the facility consumes as much energy for cooling, lighting, and power distribution as for actual computing. The global average PUE in 2025 was approximately 1.58, while best-in-class hyperscale facilities achieve 1.08 to 1.12. Older enterprise data centers typically operate at PUEs of 1.8 to 2.2, representing significant efficiency improvement opportunities. PUE has limitations as a standalone metric since it does not account for IT equipment utilization, meaning an efficient building housing underutilized servers may have excellent PUE but poor overall resource efficiency.

Carbon-Free Energy (CFE) Matching tracks the percentage of data center electricity consumption matched by carbon-free energy sources on an hourly basis within the same grid region. This approach, pioneered by Google's 24/7 Carbon-Free Energy initiative, goes beyond annual renewable energy certificate (REC) purchasing by requiring temporal and geographic matching. Google achieved 64% global CFE matching in 2023, with individual facilities ranging from 17% to 97% depending on grid conditions. Microsoft and Amazon have adopted similar commitments, with Microsoft targeting 100% 24/7 CFE by 2030.

Water Usage Effectiveness (WUE) measures liters of water consumed per kWh of IT energy. Evaporative cooling systems, while energy-efficient, can consume 1.8 to 3.0 liters per kWh, creating water stress in arid regions. Air-cooled and liquid-cooled alternatives reduce or eliminate water consumption but may increase energy use. The trade-off between energy efficiency and water consumption represents a critical design decision, particularly for facilities in water-stressed regions across Southern Europe, the Middle East, and parts of North America.

Embodied Carbon accounts for the greenhouse gas emissions associated with manufacturing, transporting, and installing data center infrastructure, including servers, networking equipment, cooling systems, and building materials. Studies estimate that embodied carbon represents 10 to 25% of a data center's total lifecycle emissions, with server manufacturing being the largest component. Extending server refresh cycles from three to five years can reduce embodied carbon by 30 to 40%, though this must be balanced against the energy efficiency gains of newer hardware.

Waste Heat Reuse captures thermal energy rejected by data center cooling systems and directs it to district heating networks, agricultural facilities, or industrial processes. Nordic countries lead this practice. In Denmark, data centers operated by Apple and Facebook supply waste heat to local district heating networks, displacing natural gas consumption. The EU Energy Efficiency Directive now requires new data centers above 1 MW to assess waste heat reuse feasibility.

Green IT Performance Benchmarks

Metric	Below Average	Average	Above Average	Top Quartile
Power Usage Effectiveness (PUE)	>1.8	1.4-1.8	1.2-1.4	<1.2
Carbon-Free Energy (% hourly)	<30%	30-60%	60-85%	>85%
Water Usage Effectiveness (L/kWh)	>2.5	1.5-2.5	0.5-1.5	<0.5
Server Utilization Rate	<15%	15-35%	35-55%	>55%
IT Equipment Refresh Cycle	<3 years	3-4 years	4-5 years	>5 years with upgrades
Waste Heat Reuse Rate	0%	0-10%	10-30%	>30%
Renewable PPA Coverage	<25%	25-50%	50-80%	>80%

What's Working

Google's 24/7 Carbon-Free Energy Program

Google has operationalized the most ambitious CFE matching program in the industry, achieving 64% global hourly carbon-free energy matching across its entire data center fleet in 2023. Their approach combines direct renewable energy procurement (over 10 GW of contracted wind and solar capacity), advanced energy storage deployments, and sophisticated load-shifting algorithms that move flexible computing workloads to times and locations with the highest CFE availability. In regions with clean grids (such as Finland and Oregon), individual facilities exceed 95% hourly CFE matching. Google published its methodology openly, enabling other organizations to adopt similar frameworks. The company targets 100% 24/7 CFE across all data centers and offices by 2030.

Equinix and Liquid Cooling at Scale

Equinix, the world's largest colocation provider with over 260 data centers globally, has deployed liquid cooling technology across its newest facilities to address the thermal demands of AI and high-performance computing workloads. Traditional air cooling struggles to dissipate heat from GPU clusters exceeding 40 kW per rack, while direct-to-chip liquid cooling efficiently handles densities above 100 kW per rack with PUE contributions approaching 1.02 to 1.05 for the cooling subsystem. Equinix's Paris 11 facility achieved a design PUE of 1.15 using a combination of direct liquid cooling and free air cooling, representing a 35% improvement over their 2018 facility average. The company has committed to 100% renewable energy across its global portfolio and achieved this target in 2023.

Stockholm Data Parks and Waste Heat Reuse

Stockholm Data Parks, a partnership between Stockholm Exergi (the city's district energy provider) and major data center operators, demonstrates industrial-scale waste heat reuse. Data centers in the program supply waste heat at temperatures between 30 and 55 degrees Celsius to Stockholm's district heating network, which serves approximately 800,000 residents. The program offers data center operators reduced electricity costs in exchange for waste heat, creating a financial incentive aligned with environmental outcomes. By 2025, data centers contributed approximately 160 GWh of heat annually to Stockholm's network, displacing fossil fuel consumption equivalent to 32,000 tonnes of CO2. Similar programs are operational in Helsinki, Amsterdam, and Dublin.

What's Not Working

Renewable Energy Certificate Arbitrage

Many data center operators claim 100% renewable energy through the purchase of unbundled Renewable Energy Certificates (RECs) that bear no temporal or geographic relationship to actual facility consumption. A facility in Virginia running on a coal-heavy grid can purchase wind RECs from Texas at $2 to $5 per MWh to claim renewable status, while its actual electricity consumption generates 400 to 500 grams of CO2 per kWh. The EU's revised guidelines on green energy claims and the GHG Protocol's ongoing Scope 2 guidance revision aim to close this gap by requiring more granular matching. Organizations evaluating data center providers should distinguish between annual REC-based claims and hourly, location-matched CFE reporting.

Water Consumption in Water-Stressed Regions

Several major data center campuses in the American Southwest and Southern Europe rely on evaporative cooling that consumes millions of liters of water annually in regions experiencing chronic water scarcity. Meta's data center in Mesa, Arizona, consumed over 4.5 billion liters of potable water in 2023. While operators are investing in recycled water sources and air-cooled alternatives, the industry's water footprint continues to grow. The tension between energy-efficient evaporative cooling and water conservation remains unresolved for facilities in arid climates.

E-Waste and Server Lifecycle Management

The data center industry generates an estimated 2 to 3 million tonnes of electronic waste annually, with server refresh cycles of three to five years driving continuous hardware replacement. Despite growing refurbishment and recycling programs, the recovery rate for critical minerals (cobalt, lithium, rare earth elements) from data center hardware remains below 30%. Extending server lifecycles through component-level upgrades (memory, storage, accelerators) rather than full replacements represents a significant opportunity, but software compatibility requirements and warranty structures often force premature hardware retirement.

Decision Framework for Evaluating Green Data Centers

Organizations assessing the sustainability of data center providers or planning internal infrastructure should evaluate options across five dimensions:

Energy Efficiency: Request facility-level PUE data (not portfolio averages) and trend lines over the past three years. Facilities achieving PUE below 1.3 demonstrate genuine engineering commitment. Ask whether reported PUE includes all facility loads or excludes items such as office space or security systems.

Clean Energy Procurement: Distinguish between annual REC matching, monthly matching, and hourly CFE matching within the same grid region. Request documentation of power purchase agreements (PPAs), on-site generation, and the methodology used for carbon accounting. The highest-integrity approach uses 24/7 hourly matching with geographic constraints.

Water Stewardship: Request WUE data and water source information. Facilities using municipal potable water for cooling in water-stressed regions represent a growing reputational and operational risk. Evaluate whether the operator has targets for water reduction or transition to non-potable sources.

Circular Economy Practices: Assess the operator's hardware lifecycle management, including server refresh cycles, refurbishment programs, component reuse rates, and e-waste disposal practices. Request data on the percentage of decommissioned hardware that is refurbished, resold, or recycled versus landfilled.

Transparency and Reporting: Evaluate whether the operator publishes annual sustainability reports with independently verified data. Look for alignment with frameworks including the EU Code of Conduct for Data Centres, the Climate Neutral Data Centre Pact, or the Open Compute Project's sustainability initiatives.

Key Players

Established Leaders

Google Cloud leads on 24/7 CFE matching with the most transparent reporting methodology in the industry. Their published Carbon Footprint tool enables customers to measure the emissions associated with their cloud workloads at regional granularity.

Microsoft Azure committed to 100% renewable energy by 2025 (achieved) and 100% 24/7 CFE by 2030. Their water positive commitment targets replenishing more water than consumed by 2030 through watershed restoration projects.

Equinix operates the largest colocation portfolio with commitments to 100% renewable energy (achieved in 2023), science-based emissions reduction targets, and industry-leading liquid cooling deployments for high-density workloads.

Emerging Startups

ECL (Echogen Clean Energy) develops waste heat recovery systems converting low-grade data center heat into electricity using supercritical CO2 power cycles, improving overall energy efficiency.

Submer provides precision immersion cooling technology that eliminates water consumption and reduces cooling energy by up to 50% compared to traditional air cooling, enabling deployment in water-stressed regions.

Lancium builds clean energy data center campuses co-located with renewable energy generation, using flexible computing loads to absorb excess renewable capacity and provide grid balancing services.

Key Investors and Funders

European Investment Bank (EIB) has financed over EUR 2 billion in sustainable data center projects across Europe, requiring compliance with the EU Taxonomy for sustainable activities.

Brookfield Renewable Partners invests in renewable energy infrastructure specifically serving data center customers, with over 5 GW of contracted capacity for hyperscale operators.

EU Innovation Fund provides grants for pioneering data center sustainability technologies, including waste heat integration and advanced cooling systems.

Action Checklist

• Audit current IT infrastructure energy consumption and establish baseline PUE, WUE, and carbon intensity metrics
• Evaluate cloud and colocation providers using hourly CFE matching data rather than annual REC-based renewable claims
• Assess water stress exposure for all data center locations using World Resources Institute Aqueduct tools
• Implement server utilization monitoring and consolidation to eliminate idle capacity consuming power without productive work
• Develop a hardware lifecycle management policy that extends refresh cycles through component upgrades where feasible
• Include Scope 3 embodied carbon from IT equipment in corporate sustainability reporting
• Evaluate waste heat reuse opportunities for owned data center facilities, particularly in regions with district heating networks
• Align data center sustainability reporting with the EU Energy Efficiency Directive requirements and CSRD disclosure standards

FAQ

Q: What is PUE and what is a good target for my organization's data center? A: Power Usage Effectiveness measures total facility energy divided by IT equipment energy. The global average is approximately 1.58, meaning 58% additional energy is consumed for cooling, power distribution, and lighting beyond what the IT equipment uses. For new facilities, target PUE below 1.3. For existing facilities, PUE improvements of 0.1 to 0.3 are typically achievable through free cooling optimization, hot/cold aisle containment, and raising inlet air temperatures. Each 0.1 PUE improvement represents roughly a 5 to 7% reduction in total facility energy consumption.

Q: How do I evaluate whether a cloud provider's renewable energy claims are credible? A: Look beyond headline "100% renewable" claims and examine the methodology. The most credible approach is 24/7 hourly carbon-free energy matching within the same grid region. Annual REC-based matching allows facilities on carbon-intensive grids to claim renewable status through certificate purchases that do not reduce actual emissions. Ask providers for their CFE percentage by region, the mix of energy sources (solar, wind, nuclear, hydro), and whether they publish independently verified data. Google, Microsoft, and Iron Mountain provide regional-level CFE disclosure.

Q: Should my organization invest in on-premises data center efficiency or migrate to the cloud? A: Cloud migration typically delivers 65 to 85% energy efficiency improvements compared to on-premises infrastructure, because hyperscale providers achieve higher server utilization rates (50 to 70% vs. 10 to 20% on-premises) and more efficient facility designs. However, cloud migration decisions involve considerations beyond sustainability, including data sovereignty, latency requirements, and total cost of ownership. For organizations retaining on-premises infrastructure, prioritize server consolidation and virtualization, which deliver the largest efficiency gains with the lowest capital investment.

Q: What is the water impact of data centers and how can it be reduced? A: Data centers using evaporative cooling consume 1.8 to 3.0 liters of water per kWh of IT energy. A 10 MW facility can consume 10 to 15 million liters annually. Reduction strategies include transitioning to air-cooled or liquid-cooled systems (which eliminate or drastically reduce water use), using recycled or non-potable water sources, and locating facilities in cool climates where free air cooling is viable year-round. Nordic locations can achieve WUE near zero through ambient air cooling for 8,000 or more hours per year.

Q: How does the EU Energy Efficiency Directive affect data center operations? A: The revised EED requires data centers with 500 kW or more of installed IT capacity to report energy performance indicators to national authorities annually, beginning May 2024. Required metrics include PUE, WUE, renewable energy share, waste heat reuse, cooling system efficiency, and server utilization rates. Non-compliance carries penalties determined by individual EU member states. The directive also requires new data centers above 1 MW to conduct waste heat reuse feasibility assessments. Organizations operating data centers in the EU should implement monitoring systems capable of generating the required metrics and establish reporting processes aligned with the European Commission's delegated regulation templates.

Sources

• International Energy Agency. (2025). Data Centres and Data Transmission Networks: Tracking Report. Paris: IEA Publications.
• Uptime Institute. (2025). Global Data Center Survey: Sustainability Metrics and Industry Benchmarks. Seattle: Uptime Institute.
• Google. (2024). 24/7 Carbon-Free Energy: Progress and Insights Report. Mountain View, CA: Google LLC.
• European Commission. (2024). Delegated Regulation on Data Centre Sustainability Indicators under the Energy Efficiency Directive. Brussels: European Commission.
• Masanet, E., et al. (2020). "Recalibrating global data center energy-use estimates." Science, 367(6481), 984-986.
• Shehabi, A., et al. (2024). United States Data Center Energy Usage Report: 2024 Update. Berkeley, CA: Lawrence Berkeley National Laboratory.
• Microsoft. (2024). Environmental Sustainability Report. Redmond, WA: Microsoft Corporation.
• Climate Neutral Data Centre Pact. (2025). Annual Progress Report: European Data Centre Industry Self-Regulation. Brussels: CNDCP Secretariat.