Imagine a data center chock full of heterogeneous equipment and running hot. That should be an easy exercise since they all are.

But now it's important to stop the waste and reduce energy consumption. Where do you start?

Well, it might be nice to whittle the problem down to size and figure out what in that sea of servers and whatnot are the biggest offenders.

A start-up called Sentilla says it can help.

It's got a wireless sensor network that can track energy use in data centers from multiple vendors, including the facility itself.

IT managers can set a baseline with the consolidated information and establish power usage effective (PUE), the first step in an energy reduction strategy.

Sentilla says its sensors, itty-bitty Java-based computers the size of a dime embedded in an intelligent power strip, can go anywhere or be attached to anything, even a blast furnace, which it's done.

The start-up, however, says the data center is the "last bastion of energy chaos."

The widgetry, which feeds data back to a Linux server for analysis via the SNMP protocol, costs $4-$8 a server a month; Sentilla claims ROI in six months; that's how it came up with its prices.

The widgetry makes recommendations and quantifies potential savings.

The upgrade, Energy Manager for Data Centers 2.1 takes data from the company's own Power Analysis Unit or other third-party equipment and consolidates it and makes it accessible from a single dashboard.

Sentilla got a $7.5 million B round in January from Onset Ventures and Claremont Creek Ventures.