Tendril, a well-known energy management startup, has just acquired a relatively obscure Massachusetts-based company, GroundedPower.

The purchase brings GroundedPower’s behavioral analytics in its Interactive Customer Engagement System into Tendril’s energy efficiency programs. If behavior analytics sounds familiar, it’s because they are. OPower leads the pack in this field and has been scooping up contracts, but competition is heating up. Besides Tendril, Silver Spring has also developed its CustomerIQ Web Portal. Tendril already has a strong foothold with utilities, locking down 38 contracts in 2010 alone. With this recent acquisition and a series D round of funding, the company is ready to take its product to the big time.

For companies focusing on behavior, it’s not just about the iPhone app (although there’s that, too). Instead, information is delivered through traditional mailings as well as through web portals. The savings aren’t that exciting (or rather, they are more exciting for utilities than consumers), usually up to 10 percent, but the rate of participation and retention are very high. Adrian Tuck, CEO of Tendril, is honest about the fact that his company, and just about everyone else, was wrong when it came to knowing what makes customers tick.

“We fell into the same trap as everyone,” he said. “Consumers don’t have information; let’s give them information. But people haven’t reacted to data the way we all thought they would. Getting to the ‘So what?’ is the next critical step.”

That critical step is integrating GroundedPower’s iCES with Tendril’s offerings. GroundedPower cut its teeth on anti-smoking campaigns with some success. If you can get people off of nicotine, surely you can get them to shave a few kilowatt-hours.

Tendril also announced that it has closed a $23 million round of series D funding, bringing its total to $73 million.

The new platform will be launched at DistribuTECH in 2011. It will be used to help utilities to offer demand response programs and monitor loads while allowing consumers to control smart devices and monitor their home energy use.

While OPower has innovated this path in the busy world of residential energy management, it is certainly no longer alone. Offering comparative information between neighbors is becoming practically necessary in any home EMS.

Tendril argues that its savings will be higher than OPower’s, closer to 10 percent than 4 percent, and higher if consumers opt into smart thermostats or demand response programs. And as for those thermostats, customers aren’t the same and Tuck argues that utilities should stop just throwing stuff at people to make them care about energy use.

“We recommend utilities stop giving people things and imagining that they want them,” he said. “Instead, give them information and then let them opt into things.”

Besides the dozens of utilities that Tendril is working with, it also has an eye on big-box stores as the market matures in coming years. The recent funding will also allow the Boulder, Co.-based company to look beyond North America into Asia, Europe and Australia in 2011.

As for Tuck’s prediction about where the market is headed in North America, look to Texas. “It will be the first North American market where [home energy management systems] are happening at scale.” Expect to see Tendril there.