Itron, North America’s biggest smart meter maker, is buying cellular smart meter leader SmartSynch for $100 million. Chalk up a big win for the cellular smart grid.

The companies announced the deal on Wednesday, and said it was expected to close in the second quarter of the year. The merger is expected to add about $50 million to Itron’s annual revenues, the Liberty Lake, Wash.-based company announced.

This may not be the most expensive smart grid acquisition so far this year. But in terms of cementing cellular networks’ place in the smart metering landscape, it’s major news. The two companies plan to merge their two platforms into Itron's OpenWay system, Philip Mezey, president and chief operating officer for Itron's global energy business, said in a Wednesday interview.

The two companies have been working together since at least 2004, with SmartSynch's communications going into Itron meters, Stephen Johnston, SmartSynch's CEO, said Wednesday. Joint customers include San Diego Gas & Electric, First Energy, West Penn Power and others, Mezey said.

Just how pleased SmartSynch's venture investors should be with the deal is less clear. The company has raised several rounds of funding, including a $20 million Series B round in 2001, a $20 million round in 2008 and $25 million of a planned $33.5 million round last year. Add it up, and it wouldn't appear that a $100 million sales price will offer a high multiple of return for that amount of investment. Johnston declined to comment on the matter Wednesday.

Jackson, Miss.-based SmartSynch has been championing cellular networks for smart meters for a decade, first with commercial and industrial meters and then at the residential level. After a few smaller-scale contracts, it landed a 1.9-million meter deployment with Michigan utility Consumers Energy in September, a $400 million project that’s led the company to plot expansions in Silicon Valley and China. Itron is now in charge of that project.

SmartSynch has also inked partnerships with Qualcomm to write applications for its 3G cellular network-enabled devices, as well as with Grid Net, the startup that’s moved from WiMax-specific smart grid networking to running software across a variety of networks. Mezey and Johnston said that Itron's acquisition of SmartSynch shouldn't have any adverse effect on those partnerships.

"We love the relationship with Qualcomm -- we think they're moving the market forward," Mezey said. Itron, for its part, has relied on wireless mesh technology to link its two-way communicating meters in neighborhood-wide networks, a choice matched by most other major vendors in North America. SmartSynch’s acquisition should “bring greater choice to utility customers across the spectrum of smart metering deployments and strengthen Itron’s integrated cellular communications offering,” the company said in a statement.

While SmartSynch only has about 130 customers, as compared to Itron’s 8,000, its technology could really help Itron reach smart meters that are hard to connect with mesh networks. That can apply to either sparsely populated rural areas that tax mesh’s limited range, or densely built urban areas that can block mesh’s lower-power signals.

We’ve seen other mesh players admit their need for cellular help. Last month, Silver Spring Networks, a champion of mesh networking, said it was adding a host of cellular options to its suite of products.

Itron also announced a new customer for its smart grid partnership with Cisco: National Grid. The U.K.-based energy company will turn to Itron and Cisco to test smart metering, home area networks and distribution automation in Massachusetts, Itron announced Wednesday.

Itron and Cisco are already working with BC Hydro in a nearly 2-million-smart-meter deployment. Just how big the National Grid project might grow, the companies didn’t say.