Ed Lu, the astronaut turned member of the engineering team behind Google's PowerMeter home energy management project, isn't sure that it will be the best solution to the world's energy efficiency challenges.

That's why Google plans to open up the gadget to the world to write applications for, as soon as possible – though Lu doesn't have a hard date on when that will happen yet.

"We're opening our APIs as soon as we can," Lu said after giving a speech Tuesday at the ConnectivityWeek 2009 conference in Santa Clara, Calif. But saying just when that might be will have to wait until Google has gone through "at least one more iteration" of the software, he said.

"We may not have the best solution," he said. "We think we have a good solution. But we'd like to se lots of entities trying to get this information out to people."

Opening up PowerMeter to outside developers – and making it free – was a key pitch for the software when Google announced the effort early this year (see Google Gets Into Home Energy Management).

Last month, Google announced it would work with smart meter maker Itron and eight utilities to bring PowerMeter to test customers at first, with an eye toward rolling it out to more customers later this year (see Google Names Itron, Utilities as PowerMeter Partners).

Google can't discuss the other partners it's working with right now, Lu said. But it intends to announce some of them at the same time it announces it is opening its APIs, he said.

The search giant hasn't revealed much about the specifics of how it will pull energy data into PowerMeter. But San Diego Gas & Electric, one of the utilities partnering on the PowerMeter effort, said it will bring the data back to its central systems, then deliver it over broadband to customers' computers.

Google has said it's interested in finding ways outside smart meters to get energy usage data to PowerMeter (see Google Looks Beyond Smart Meters for Home Energy Data).

But Lu said Tuesday that the company was not now looking at partnerships with utilities that didn't already have substantial smart meter deployments underway, although eventually Google would like the platform to be available to any utility to use in a do-it-yourself manner.

Nor does Google find getting a power reading from every appliance in the home that valuable a proposition, Lu said. Instead, "We ask the user," he said.

"People have very little difficulty identifying the peaks" in power use by major home appliance or system, he said. Outside of that, "The small stuff doesn't amount to much."

Still, Lu added, Google is interested in finding out what extra value the "small stuff" might bring to consumers understanding of home energy use – which is where the third-party developers come in.

"We're not going to do it, but we're going to make it easy for other people to do," he said.

That could come from home energy management startups like Tendril Networks, Greenbox, Gridpoint, Control4 and others. Or, it could come from someone Google hasn't heard of, Lu noted.

"There are quite a few of those companies," he said. "But that makes it exciting."