It’s so hot, in fact, that data centers – those expensive warehouses full of computers that serve up information – are racking up huge power bills. According to Hewlett-Packard’s (HPQ) calculations, a large data center with 70,000 square feet of space might guzzle $10.4 million worth of power in a year. Data centers require so much energy that over a three-year period, the computers inside could easily cost a company as much to plug in and cool as they did to purchase in the first place.

To deal with the power problem, and make some money in the process, HP weeks ago began selling a homegrown technology called Dynamic Smart Cooling. Today, the company is releasing numbers it hopes will convince customers that the technology works.

When HP installed a Dynamic Smart Cooling system in a data center in Bangalore, it managed to cut cooling costs by 40 percent. If those results bear out in other settings, companies that operate multiple data centers could see millions of dollars in savings.

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John Sontag, director of virtualization and datacenter architecture for HP Labs, said HP had previously offered cooling numbers based on an installation in a tiny 3,000-square-foot U.S. data center. He expects that these numbers will be more convincing. “We’ve had a strong belief all along that our solution would scale,�� he said.

Dynamic Smart Cooling works something like a high-tech home thermostat. In a typical big-company installation, thousands of tiny sensors measure how much heat computers in a data center give off. The sensors then pass the information to an intelligent air conditioning system that decides which areas of a vast server farm need to be cooled, and how much.

That method is different from the standard practice in data centers, which is to blast air conditioners all the time. Like a thermostat that cools a home only when it’s hottest and when people are home, the flexible approach of Dynamic Smart Cooling uses less energy.

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HP estimates that it will typically take five months from when it initially briefs a customer on Dynamic Smart Cooling to when a customer flips the switch and begins using the technology.

HP is one of several companies, including Intel (INTC), Advanced Micro Devices (AMD), and Sun Microsystems (JAVA), looking for ways to make data centers more efficient. And the market for efficient technology will probably be around for a while: According to the Department of Energy, U.S. data centers accounted for 1.5 percent of country’s electricity use last year, more than all the color televisions combined.

As long as companies like Apple (AAPL) Google (GOOG), Yahoo (YHOO) and Microsoft (MSFT) keep investing in audio, video and social networking services, there will be demand for more data centers.