Burlingame, Calif.-based startup Sentient Energy has been quietly earning a reputation for its low-cost grid sensor technology -- and its deep partnership with big smart grid networking startup Silver Spring Networks.

On Thursday, the two companies opened the curtain on that partnership, announcing that Sentient’s Master Monitor 2 (MM2) sensors, the “industry’s most advanced faulted circuit indicator,” are now for sale with Silver Spring’s radios inside.

Silver Spring, which connects some 12 million smart meters and counting in the United States, with another 6 million or so under contract, is reselling the MM2 sensors, and has also upgraded its network management software to support it across the breadth of its deployments, starting this week.

That’s not to say the two haven’t been working together for some time now. We’ve been hearing that the two have been deploying together for more than a year, though neither company would talk about it. Michelle Rae McLean, Silver Spring’s director of product marketing, wouldn't name any customers during a Thursday interview, but she did say that there are multiple utilities using Sentient's devices over Silver Spring's network, some of them with hundreds of sensors deployed.

Now the industry can get a peek under the hood. Here’s what the two are promising:

A Sensor that Powers Itself

First of all, Sentient provides hints of how it achieves lower costs than competing grid sensors on its web page describing its MM2 device. Simply put, it does away with a good share of the cost of deploying a sensor by attaching to the wire it’s going to monitor, and then drawing its power from it.

To wit: “The MM2 generates its own power from the electro-magnetic field around the conductor, As such, no RTU, secondary power connection or pole attachment is required.” That makes for deployment that’s “very cost effective, taking only minutes to install and designed for zero physical maintenance.”

In fact, Sentient devices can be deployed via a “hot stick” method -- that is, dropped onto a power line by a worker holding an insulated stick, McLean said. That's a lot faster and less expensive than calling out bucket trucks and sending workers up utility poles to install them, she said.

As for drawing power from the line itself, there are a few other companies using similar inductive powering technologies for their grid sensors, McLean said. But Sentient also has a battery backup to cover times when the power goes out -- an important consideration for fault detection, she noted. Sentient also goes beyond the “I’m up or I’m down” signals typical of simpler devices, measuring current, temperature and power quality, as well as tracking those factors over time, she said.

Distribution grids are more or less blind to utilities today past the substation, but adding sensors can bring all kinds of benefits, from pinpointing faults for faster repairs to analyzing loads to replace lines or transformers that are about to fail. GTM Research predicts that the U.S. distribution automation market will rise from $1.75 billion in 2010 to about $3 billion in 2015, outpacing smart meters in terms of money spent.

Still, utilities have to think of costs when putting up DA networks -- and having an easy-to-install sensor like Sentient’s ride on the power of the line it’s monitoring could help. Making sensors an incremental cost addition to an existing Silver Spring smart meter networking deployment could reduce those costs further.

McLean declined to disclose how much the Silver Spring-enabled Sentient sensors cost, but expects that line-powered devices integrated to an existing network could be about a third less expensive than competing systems.  We’ve heard reports that Sentient’s device cost about $250 and that Silver Spring’s comms modules add about another $250 to that cost, though that’s just speculation.

A Beefed-Up Network for DA

Second, Silver Spring has enhanced its GridScape network management application to support Sentient’s devices, according to Thursday’s press release. Specifically, it’s launching GridScape 1.3, a platform that’s meant to connect smart meters, sensors, and all the other devices Silver Spring wants to integrate into its networks in the future.

GridScape for DA, according to Silver Spring’s website, connects the company's Bridge units that link up to RTUs, relays and other grid-side devices, to map and monitors the flows of data across the network itself as well as the grid it’s monitoring.

In other words, it sounds a lot like Silver Spring’s answer to network management platforms from the likes of Cisco, SK Telecom’s GridMaven, startup Proximetry Networks and all the other companies that deploy wireless networks on the grid. Silver Spring has qualified to network certain DA devices from the likes of ABB, Schweitzer and many others, and is doing a big DA project with AEP Ohio. But it wants to expand grid sensor and control capabilities to a broader customer base.

Beefing up its network management system to handle the kinds of fast-response, mission-critical grid functions that DA calls for may be an important step toward realizing those goals. Notably, Sentient says its MM2 can also be hardware-configured to act as a mesh relay for the 900-megahertz Silver Spring network it’s connected to. The two companies didn’t specify what other communications options are available for the MM2, though Silver Spring is building cellular connectivity into its latest devices, a nod to the growth in popularity (and falling price) of public networks as an option for smart grid deployments.

A Long-Running -- and Possibly Exclusive -- Partnership

Third, Sentient and Silver Spring seem to be pretty much wedded at the hip. Indeed, McLean said that Sentient has built its sensors specifically for Silver Spring, and isn’t shipping with any other customers to date. Sentient announces on its Web site that it can “integrate seamlessly with any Silver Spring AMI or Distribution Automation network,” a level of integration it doesn’t advertise with any other vendors. The two also share a common investor in Foundation Capital, indicating another potential layer of alignment between the two companies and their goals.

Of course, Sentient is one of many partners with the Silver Spring, which wants to expand its massive base in smart meters to include demand response, plug-in vehicle charging and various distribution grid automation functions.

That’s seen as a key to growing revenues from existing investments, and helping the company achieve profitability -- particularly if it’s going to pull the trigger on its long-awaited plans to raise as much as $150 million in an initial public offering.

Silver Spring reported 2011 revenues of $237.5 million, more than triple its 2010 revenues of $70.2 million. Still, it hasn’t yet seen profits from its ongoing business: it lost $92.36 million in 2011, down from $148.45 million in 2010.

Most of its deployments are with a few key U.S. customers like Pacific Gas & Electric, Pepco, Oklahoma Gas & Electric, Commonwealth Edison and Progress Energy, but the 10-year-old company is also branching into international markets, in Australia since 2009 and more recently in Brazil. It has raised nearly $400 million, with recent investors EMC and Hitachi coming on board.

As for Sentient, it was founded in 2009, and while it has remained quiet about how much money it has raised, Link Silicon Valley reports the company has raised $7.1 million. In 2010, Sentient was one of 12 winners splitting $55 million from GE’s Ecomagination Challenge. GTM Research named Sentient one of its runners-up on its Smart Grid Players to Watch in 2012 list.

The company is led by CEO Michael Bauer, a former Entrepreneur in Residence at Oak Ridge National Laboratory for the Department of Energy and Foundation Capital, whose prior work includes smart grid experience with BPL Global and broadband and video networking in Silicon Valley.

Michael Kast, VP and founder, is a veteran of sensor companies like EnergyLine (now part of S&C Electric) and Gridcom, a startup that worked on line sensors with Pacific Gas & Electric in the 1990s, and CTO Mark Parsons has worked on ruggedized sensors for Maxim Integrated Products and Ford Microelectronics Research.