Data Center Cooling Energy Efficiency Retrofit: Practical Steps for Existing Facilities

A data center cooling energy efficiency retrofit is one of the most cost-effective ways to cut operating expenses in an existing server room. Many facilities run their cooling systems at conservative settings that waste power, and simple changes—like raising setpoints or improving airflow—can reduce cooling energy by 20-30% without compromising equipment reliability. This article walks through the practical steps you can take, from measurement to implementation, to lower your PUE and your electricity bill.

Why Retrofit Existing Cooling Instead of Replacing Everything?

Replacing an entire cooling plant is expensive and disruptive. A retrofit works with what you already have, targeting inefficiencies that creep in over time. Older CRAC units often run at fixed speeds, overcool the space, or have worn components that reduce efficiency. Fixing these issues can extend the life of your equipment and defer capital spending.

Plus, the payback on many retrofits is measured in months, not years. For example, simply cleaning coils and filters can improve heat exchange efficiency by 5-15%, depending on how dirty they are. That’s a low-cost maintenance task that pays for itself almost immediately.

Start with Measurement and Verification

Before changing anything, you need a baseline. Measure your current cooling energy use, inlet temperatures at the equipment, and humidity levels. Use this data to calculate your current PUE and identify where the biggest inefficiencies are.

1. Install temporary or permanent sensors to log temperature and humidity at multiple points, including rack inlets and return air.
2. Track the energy consumption of each CRAC unit separately, not just the total facility power.
3. Record runtime hours, setpoints, and any alarm history for each unit.

After you implement changes, measure again under similar load conditions. Compare the before-and-after numbers to quantify savings. This also helps you catch any unintended side effects, like hot spots that develop after you raise setpoints.

Raise Temperature Setpoints Within Equipment Limits

ASHRAE’s thermal guidelines allow inlet temperatures up to 27°C (80.6°F) for most IT equipment, with some classes allowing even higher. Yet many facilities still cool to 20°C or below. Every degree you raise the setpoint can cut cooling energy by 3-5%, because the compressors and fans work less hard.

Check the manufacturer specs for your servers and storage equipment to confirm the allowable inlet range. Then, increase the return air setpoint in small steps—say 1°C at a time—and monitor inlet temperatures at the racks to ensure they stay within limits. This is a classic data center cooling energy efficiency retrofit that requires no hardware changes.

Reduce Overcooling and Unnecessary Dehumidification

Many CRAC units dehumidify even when humidity is already within acceptable range. This happens when the dew point setpoint is too low or when the cooling coil runs colder than necessary. Dehumidification is energy-intensive because it re-heats the air afterward.

Check your humidity setpoints. ASHRAE recommends a dew point range of 5.5°C to 15°C (42°F to 59°F) for most data centers. If you’re maintaining a tighter range, widen it to the recommended envelope. Also, ensure that the cooling coil temperature is not set lower than needed to meet the dew point. In some cases, you can disable the humidifier and dehumidifier entirely if the local climate keeps humidity naturally in range.

Improve Airflow Management

Poor airflow is a silent killer of efficiency. Hot air recirculating back into the equipment forces the cooling system to work harder. Simple fixes—like installing blanking panels in empty rack spaces, sealing cable openings, and arranging rows in a hot aisle/cold aisle layout—can make a big difference.

• Install blanking panels to prevent hot air from bypassing the cooling path.
• Use grommets or fire-resistant sealant to close cable cutouts in the floor.
• Arrange racks so that cold aisles face the CRAC supply and hot aisles face the return.

If you have a raised floor, check for leaks and ensure perforated tiles are placed only in front of racks that need airflow. In a non-raised floor environment, consider adding ducting or containment to direct air where it’s needed.

Clean Coils and Filters, Repair Worn Components

Dirty coils and clogged filters reduce heat transfer and increase fan energy. A simple cleaning can restore efficiency. Check coils for dust, debris, and bent fins. Clean them with a soft brush or compressed air, being careful not to damage the fins. Replace filters according to the manufacturer’s schedule, and consider using higher-efficiency filters if the pressure drop is acceptable.

Also, inspect fans and compressors for wear. Worn belts, misaligned pulleys, or failing bearings can increase energy use and reduce cooling capacity. Repair or replace these components before they cause a breakdown. This is basic maintenance, but it’s often overlooked in busy facilities.

Add Variable Speed Drives

Many older CRAC units run fans and compressors at full speed regardless of load. Retrofitting variable speed drives (VSDs) allows the system to modulate output to match the actual cooling demand. This can cut fan energy by 30-50% during partial load conditions, which is most of the time.

VSDs can be added to existing units, but you need to ensure the motor and controller are compatible. Work with a qualified electrician or your HVAC vendor to size the VSD correctly. The savings are often significant enough to justify the retrofit cost within a year or two.

Implement Containment and Smarter Scheduling

Containment is a step beyond basic airflow management. By physically separating hot and cold aisles with panels or curtains, you prevent air mixing and allow higher supply temperatures. This can reduce cooling energy by 10-20% on top of other measures.

Scheduling is another low-cost measure. If your facility has predictable load patterns, you can adjust cooling capacity during off-peak hours. For example, if you have redundant CRAC units, you might turn off one during low load periods, as long as you maintain required redundancy and monitor temperatures. This is a data center cooling energy efficiency retrofit that requires no hardware, just smart control.

Monitor and Adjust Continuously

A one-time retrofit is not enough. After you make changes, continue to monitor temperatures, humidity, and energy use. Use the data to fine-tune setpoints and schedules. You might find that you can push the setpoint higher after you improve airflow, or that a particular unit runs inefficiently and needs attention.

Also, keep records of your PUE over time. A good PUE for an existing facility is around 1.5 or lower, but the goal is to improve from your baseline, not to hit a specific number. Every percentage point of improvement translates into real cost savings.