What is PUE and Why Lighting Matters for Data Centers

In the digital age, data centers stand as the backbone of global connectivity, powering everything from cloud storage to real-time communication. PUE is an important metric to measure the energy efficiency of a data center. Although lighting is a small part of energy consumption, it is also crucial for optimizing data center PUE. 
In this article, we’ll understand what PUE is and why lighting matters for data centers. This article also provides practical tips to help you lower PUE by upgrading lighting solutions.

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Power Usage Effectiveness (PUE) is a metric developed by The Green Grid to measure the energy efficiency of a data center. It measures how much of the data center’s total energy is actually used to run its IT equipment like servers, storage devices, and networking gear.

PUE is a critical benchmark because it directly reflects operational efficiency. A lower PUE means more energy goes to running the main IT equipment, which helps cut down on waste and saves money. For example, if a data center has a PUE of 1.3, it uses 30% more energy than its IT equipment actually needs. A PUE of 1.8 means 80% more energy is used on things other than IT. Even small changes in PUE can lead to big savings. If a center uses 100 MW for IT, lowering the PUE from 1.5 to 1.4 could save 10 MW of energy each year.


A PUE of 1.0 is theoretically perfect, meaning all energy entering the data center is used exclusively by IT equipment. In reality, no data center achieves this. This is because energy is required for supporting systems such as cooling, ventilation, power distribution, lighting, and security. Most data centers have a PUE between 1.2 and 1.8, though inefficient data centers can exceed 2.0 or higher.

To calculate PUE accurately, you need to carefully track and organize energy use over a set time period, like a month, a quarter, or a year. The process has two main steps: first, measure the total energy the entire data center uses; second, measure how much of that energy goes specifically to the IT equipment.

• Total Data Center Energy: It encompasses energy for IT equipment, cooling systems, power distribution units, uninterruptible power supplies, lighting, security systems, and any auxiliary equipment like office spaces within the data center.
• IT Equipment Energy: This refers specifically to energy used by the core IT infrastructure, including servers, storage arrays, switches, routers, and other devices directly involved in data processing and transmission.

However, there are other important considerations to ensure reliability.

• Both total data center energy and IT energy must be measured over the same time frame to avoid skewed results.
• If the data center uses on-site renewable energy like solar panels, that energy should still be counted in the total facility energy, since it adds to the overall amount being used.
• PUE can change with the seasons. For example, cooling systems use more energy in the summer, which increases total energy use and makes the PUE higher. That’s why yearly averages usually give a better picture than short-term measurements.

Cooling systems typically account for the largest share of non-IT energy use, which is often 30-50% of total data center energy. However, lighting is usually an underestimated component. Actually, it plays a vital role in both operational efficiency and workplace safety. Here’s why lighting deserves attention in data center design and management.
 

Traditional lighting, such as fluorescent tubes or high-intensity discharge (HID) lamps, consumes more energy and has shorter lifespans than modern alternatives. 
For example, a 100,000-square-foot data center using fluorescent lights might use 50 to 100 kW of power just for lighting. In one year, that adds up to 438,000 to 876,000 kilowatt-hours, which increases the overall energy use and makes the PUE higher.

Lighting emits heat, which adds to the cooling burden of data centers. Traditional lighting sources, such as incandescent bulbs, convert only 10% of energy into light, wasting 90% as heat. 

The excess heat forces cooling systems to work harder, increasing their energy consumption and, in turn, raising PUE. In a data center where cooling accounts for 40% of non-IT energy, reducing lighting-related heat by 70% could cut cooling energy use by 5–10%, further improving PUE.

Data centers require high-quality lighting to ensure safe and efficient operations. Technicians and engineers often work in server rooms, aisles, and utility areas to do maintenance, fix problems, or install equipment. 

If the lighting is poor, it can lead to accidents like tripping or using equipment the wrong way. It also makes their work slower, which can cause longer downtime.

As governments and industries tighten regulations on carbon emissions and energy efficiency, data centers face growing pressure to reduce their environmental impact. Lowering data center PUE is a key strategy for meeting these requirements. Optimizing lighting is a tangible step toward that goal.

Strategic upgrades to data center lighting systems can deliver measurable reductions in PUE. Here are the key steps to achieve this.

The most impactful step in reducing lighting-related energy use is replacing traditional lighting with LED fixtures. LEDs use up to 75% less energy than incandescent bulbs and 50% less than fluorescent lights. By switching to LEDs, which emit less heat than incandescent or fluorescent bulbs, data centers can reduce their cooling energy use. This helps reduce the total energy used by the data center, which lowers the PUE.

Beyond energy savings, LEDs have longer lifespans, which reduces maintenance costs and downtime associated with bulb replacements. LEDs also last a long time, which fits well with how data centers operate, as their equipment often runs nonstop for years.

Even the most efficient LEDs waste energy if left on in unoccupied areas. Smart lighting systems ensure that lighting is only active when and where it’s needed. 

Occupancy sensors: When placed in server aisles, utility rooms, and maintenance corridors, these sensors can detect when people are around and automatically turn the lights on or off.
Daylight harvesting: If a data center has windows or skylights, such as in office areas, sensors can dim the lights when there’s enough natural light
Centralized Management: Integrating lighting controls with the data center’s Building Management System (BMS) allows operators to monitor and adjust lighting remotely.

Different parts of a data center need different types of lighting. Server racks need focused light for maintenance, while shared areas need wider light coverage. Using lights that are too bright wastes energy and creates extra heat.

• Task Lighting: Install targeted LED lights above server racks or workstations to give technicians the bright, focused light they need in those areas.
• Zoned Lighting: Split the data center into zones like IT halls, cooling rooms, and break areas, and set lighting levels based on function.

Optimizing PUE through lighting solutions is no longer just an option. It’s a necessary step to achieve significant energy savings. When it comes to data center lighting, LEDVANCE stands out as a trusted provider of fixtures. Our lighting products are designed to deliver measurable PUE reductions through these features:

• Smart Control
• Dimmable
• Product Variety

LEDVANCE’s data center lighting portfolio includes high-performance LED fixtures tailored to different zones. With excellent energy efficiency, our LED emits minimal heat to reduce the strain on cooling infrastructure, further contributing to PUE improvements.

If you seek a turnkey solution for data centers aiming to lower PUE, contact us to discuss further details and more personalized lighting design.