Retrofitting a data center to make it more energy efficient has its restrictions, but doing so can be less costly than having to rebuild an entire facility. To weigh the variables—and achieve energy cost savings – you need to know what’s broken. Here are five tips for determining the efficiency of your data center and how to make it green as can be.

1. Get to know your data center.
An energy efficiency assessment from someone who specializes in data centers should be a priority, says Neil Rasmussen, CTO of American Power Conversion (APC), a provider of data center power and cooling equipment. IBM, EYP Mission Critical, Syska Hennessy, APC and Hewlett-Packard offer such services.

HP recently added Thermal Zone Mapping to its assessment offering. This service uses heat sensors and mapping analysis software to pinpoint problem areas in the data center and helps you adjust things as needed, says Brian Brouillette, vice president of HP Mission Critical Network and Education Services. For example, the analysis looks at the organization of equipment racks, how densely the equipment is populated, and the flow of hot and cold air through different areas of the space. It’s important to place air-conditioning vents properly so that cool airflow keeps equipment running properly, without wasting energy, says Brouillette.

2. Manage the AC: Not too cold, not too hot, but just right.
Energy efficiency often starts with the cooling system. “Air conditioners are the most power hungry things in the data center, apart from the IT equipment itself,” says Rasmussen. If your data center is running at 30 percent efficiency, that means for every watt going into the servers, two are being wasted on the power and cooling systems, he says. To reduce wasted energy, one of the simplest and most important things you can do is turn on the AC economizers, which act as temperature sensors in the data center. According to Rasmussen, 80 percent of economizers are not used, just as IT administrators often turn off the power management features in PCs. It’s also important to monitor the effects of multiple air-conditioning systems attached to a data center; sometimes, Rasmussen says, two AC systems can be “out of calibration” one sensing humidity is too high and the other sensing it'stoo low; their competition, like a game of cooling tennis, can waste energy.

Richard Siedzick, director of computer and telecommunications services at Bryant University, uses such features in his data center. “If the temperature rises to a certain level, the AC in that rack will ramp up, and when it decreases, it will ramp down.” The result is a data center climate that few are used to. Instead of being met with an arctic blast at the door, Siedzick says people have told him his data center is too warm. That’s not actually the case: AC economizers help cooling stay where it is needed, rather than where it is not. And that means increased efficiency and monetary savings. “We estimate we've seen a 30 percent reduction in energy [in part, due to more efficient cooling] and that translates into $20,000.” Siedzick says other precision controls, such as humidity sensors, are used in the data center as well.