Datacenters consume between 1% and 2% of global electricity, a figure that grows every year driven by demand for cloud computing, artificial intelligence and digital services. In the European Union, data centres account for approximately 2.7% of total electricity consumption, and projections indicate this could reach 3.5% by 2030 if aggressive efficiency measures are not adopted.
Energy efficiency is no longer just a matter of reducing operational costs: it is a regulatory obligation, an environmental commitment and a competitive factor. Enterprise clients increasingly demand transparency about the carbon footprint of their infrastructure providers, and European regulations impose mandatory reporting requirements and minimum efficiency standards.
In this article we explain the metrics, technologies and practices that define an energy-efficient datacenter: from the PUE formula to immersion cooling, including renewable energy, sustainability certifications and EasyDataHost's commitment to efficiency at its data centre.
What Is PUE (Power Usage Effectiveness)
PUE (Power Usage Effectiveness) is the industry standard metric for measuring datacenter energy efficiency. It was defined by The Green Grid in 2007 and subsequently adopted as the ISO/IEC 30134-2 standard. PUE expresses the ratio between the total energy consumed by the facility and the energy that actually reaches IT equipment.
A PUE of 1.0 would mean that all energy is dedicated exclusively to computing equipment, with no losses from cooling, lighting or power distribution. In practice, this is unattainable: there is always an energy overhead associated with maintaining environmental conditions and support infrastructure.
PUE Formula and Efficiency Tiers
The PUE formula is straightforward:
PUE Formula:
PUE = Total Facility Energy / IT Equipment Energy
Total facility energy includes everything the facility consumes: servers, storage, networking, cooling, lighting, security systems, UPS and transformers. IT energy only accounts for what reaches computing, storage and networking equipment. The difference between the two is the infrastructure overhead.
- error PUE 2.0 - Inefficient: for every watt dedicated to IT, another watt is consumed in overhead. Typical of legacy facilities without cooling optimisation or efficient power distribution.
- info PUE 1.5 - Industry average: overhead represents 50% of IT consumption. Many commercial datacenters operate in this range with well-managed conventional cooling systems.
- check_circle PUE 1.2 - Excellent: only 20% overhead. Requires free cooling, optimised power distribution and advanced thermal management. This is the target for well-designed modern datacenters.
- star PUE 1.0 - Perfect (theoretical): zero overhead. Unattainable in practice, but hyperscalers like Google report PUEs of 1.10-1.12 at their best facilities.
Cooling Systems
Cooling accounts for between 30% and 50% of a datacenter's non-IT energy consumption, making it the primary target for optimisation. There are four main approaches, each with different levels of efficiency and complexity:
- ac_unit CRAC/CRAH (precision air conditioning): climate control units specifically designed for datacenters that maintain constant temperature and humidity. It is the most widespread system but also the least efficient. It is combined with hot/cold aisle containment to optimise airflow and prevent recirculation.
- air Free cooling: uses cold outside air to cool the room without compressors. It works when the outside temperature is lower than the datacenter's target temperature. In temperate climates such as central and northern Europe, it can cover more than 80% of annual cooling hours, drastically reducing PUE.
- water_drop Liquid cooling (direct liquid cooling): delivers coolant directly to CPUs and GPUs via contact blocks or cold plates, eliminating air as an intermediary. Up to 70% more efficient than air cooling for high-density workloads such as AI and HPC clusters.
- waves Immersion cooling: submerges entire servers in a non-conductive dielectric fluid. It completely eliminates server fans and can reduce cooling energy consumption by up to 95%. It is the most efficient technology but requires compatible hardware and specialised tanks.
Cooling Systems Comparison
The following table compares the four main cooling systems in terms of efficiency, cost and applicability:
| Criterion | Air (CRAC) | Free Cooling | Liquid Cooling | Immersion |
|---|---|---|---|---|
| Typical PUE | 1.5 - 2.0 | 1.15 - 1.3 | 1.1 - 1.2 | 1.02 - 1.10 |
| CAPEX | Low | Medium | High | Very high |
| Energy OPEX | High | Low | Very low | Minimal |
| Supported density | Up to 10 kW/rack | Up to 15 kW/rack | Up to 50 kW/rack | Up to 100+ kW/rack |
| Climate dependency | None | High (requires cold climate) | None | None |
| Ideal use case | Legacy DC, low density | New DC in temperate climates | HPC, AI, GPU clusters | Edge, extreme high density |
Power Distribution: UPS, PDU and Transformers
The power distribution chain from the utility feed to the server introduces losses at every stage. Optimising this chain is critical for reducing PUE, as each percentage point of distribution efficiency translates directly into permanent energy savings.
UPS (Uninterruptible Power Supply) systems are the component with the greatest impact on distribution losses. Traditional double-conversion UPS units operate at 90-94% efficiency, meaning between 6% and 10% of all energy passing through them is converted to waste heat. Modern UPS systems with eco-mode or interactive mode achieve efficiencies of 98-99% by bypassing the inverter under normal conditions, activating full conversion only during a power outage.
Intelligent PDUs (Power Distribution Units) with outlet-level monitoring allow identification of underutilised or abnormally consuming servers. Combined with efficient backup generators, they form the backbone of a resilient and optimised electrical infrastructure. Transformer losses are minimised by using high-efficiency units and correctly sizing the load to avoid operation at low-efficiency ranges.
Renewable Energy and Decarbonisation
Reducing PUE is not enough if the energy powering the datacenter comes from fossil fuels. Full decarbonisation requires that all energy consumed be from renewable sources, whether generated on-site or procured through verifiable market mechanisms:
- solar_power Solar photovoltaic: solar panels on datacenter rooftops and car parks. Generates energy during peak demand hours (midday) but does not cover nighttime. It is a complementary source that can cover between 10% and 30% of total consumption depending on location and available surface area.
- wind_power Wind: dedicated or co-owned wind farms that supply green energy directly or through the grid. Wind complements solar by producing more energy at night and during winter.
- handshake PPA (Power Purchase Agreement): long-term contracts (10-20 years) with renewable energy producers that guarantee a fixed price and 100% green supply. It is the preferred mechanism for large datacenter operators because it offers price certainty and source traceability.
- verified RECs and Guarantees of Origin: certificates that attest that an equivalent amount of renewable energy has been injected into the grid. They are the most accessible mechanism for mid-sized operators who cannot sign direct PPAs.
EU Regulations: EED and EU Taxonomy
The European Union has significantly tightened regulation on datacenter energy efficiency. The revised Energy Efficiency Directive (EED) of 2023 requires all datacenters with an installed IT capacity exceeding 500 kW to report annually on their PUE, water consumption, use of renewable energy, reuse of waste heat and operating temperature.
The EU Taxonomy for sustainable finance classifies economic activities according to their contribution to climate change mitigation. For an investment in a datacenter to be classified as "sustainable", the facility must demonstrate a PUE below 1.3 (in cold climates) or 1.4 (in warm climates), implement water management measures and use refrigerants with low global warming potential.
Reporting obligation:
Since 2024, European datacenters with more than 500 kW of IT capacity must report their energy efficiency indicators to the European Commission database. Non-compliance can result in financial penalties and exclusion from green financing programmes.
Sustainability Certifications
Certifications provide a verifiable framework for demonstrating a datacenter's commitment to energy efficiency and sustainability. The most relevant in the European context are:
- eco LEED (Leadership in Energy and Environmental Design): a sustainable building certification that evaluates energy efficiency, water management, materials and indoor air quality. A datacenter with LEED Gold or Platinum demonstrates that the building has been designed and built with comprehensive sustainability criteria.
- assignment ISO 50001: an energy management system that establishes a framework for continuous improvement in reducing energy consumption. It requires systematic monitoring, goal setting, action plans and regular audits. It is the certification most focused on day-to-day operations.
- policy EU Code of Conduct for Data Centres: a voluntary code from the European Commission that defines best practices for datacenter energy efficiency. It covers design, construction, operation and monitoring, and is periodically updated to reflect the latest available technologies.
Circular Economy: Hardware Lifecycle
Datacenter sustainability does not end with PUE. The complete hardware lifecycle -- from manufacturing to decommissioning -- has a significant environmental impact. The circular economy applied to datacenters seeks to maximise equipment lifespan, minimise waste and recover valuable materials.
Extending server lifespan is the most impactful measure. A server that operates for 6-7 years instead of the traditional 3-4 halves the embodied carbon footprint per year of service. Refurbished outlet servers and high-performance refurbished hardware are a sustainable alternative that extends the hardware lifecycle without sacrificing performance.
Responsible e-waste management requires a certified recycling chain that recovers precious metals, plastics and reusable components. Datacenters committed to the circular economy establish agreements with R2 or e-Stewards certified recyclers and maintain traceable records for every piece of decommissioned equipment.
EasyDataHost and Sustainability
EasyDataHost integrates energy efficiency as a core principle in the design and operation of its data centre. The colocation infrastructure is designed to maximise cooling efficiency and minimise power distribution losses, with an ambitious PUE target and continuous monitoring of all energy parameters.
- check_circle Efficient cooling: aisle containment systems and free cooling that reduce climate control energy consumption.
- check_circle High-efficiency UPS: uninterruptible power supply systems with eco-mode to minimise conversion losses.
- check_circle Outlet hardware: a programme of refurbished servers that extends equipment lifespan and reduces the carbon footprint.
- check_circle Managed services: continuous monitoring and optimisation of infrastructure to maintain maximum operational efficiency.
Conclusion
Datacenter energy efficiency has evolved from an optional aspiration into a regulatory requirement, an economic imperative and a client expectation. PUE is the reference metric, but true sustainability demands a holistic approach encompassing cooling, power distribution, renewable energy, certifications and the circular economy.
- arrow_right PUE measures the ratio between total energy and IT energy: 1.2 is excellent, 2.0 is inefficient.
- arrow_right Cooling is the main non-IT consumer: free cooling, liquid cooling and immersion offer drastic reductions.
- arrow_right EU regulations (EED, EU Taxonomy) require mandatory reporting and maximum PUE for sustainable finance.
- arrow_right Certifications such as LEED, ISO 50001 and EU Code of Conduct validate the commitment to sustainability.
- arrow_right EasyDataHost integrates energy efficiency, refurbished hardware and continuous monitoring into its infrastructure.
If you need efficient and sustainable datacenter infrastructure for your business, contact our team to design the solution that best fits your performance and sustainability requirements.