Solar panel integration is something of a holy grail for companies like SolarBridge, ArrayPower, SolarEdge, Tigo and other startups in the decentralized solar power electronics field. After all, what better testament to the proposition that distributed optimizers, AC modules or microinverters are worth their extra costs than seeing them as part of the panel itself?

Thus, we’ve seen startups like SolarBridge partner with SunPower and ArrayPower partner with Canadian Solar as they seek to one-up microinverter makers with a frame-attached AC solar modules. At the same time, microinverter market leader Enphase is doing frame-attached projects with Upsolar and Hanwha SolarOne, as it and other microinverter makers like SMA, Power-One, Enecsys and more seek to establish themselves more deeply with panel partners.

On the truly panel-embedded front, DC optimizer startup Tigo Energy announced last year that solar panel makers Trina Solar, Hanwha and Upsolar will be integrating Tigo’s maximum power point tracking into its panels. But there’s a long road between launching a product and finding mass-market acceptance.

First, panel makers and their partners will have to prove that frame-attached or embedded power electronics don’t cause reliability or performance problems. Then, they can start to worry about whether or not the extra cost per panel -- currently about 10 to 25 cents for Tigo -- will find its value being recognized by eager buyers, or get the cold shoulder in the marketplace.

On Tuesday Aug. 28, a GTM Research-moderated webinar, “Quantifying the Impact of Module Level Power Electronics,”  will be taking a deeper dive into these topics. In the meantime, Tigo passed a couple more mileposts on its quest for panel-embedded bankability this month.

First, the Los Gatos, Calif.-based startup announced that engineering firm BEW has approved its PV optimizer as “suitable for deployment in commercial and utility-scale bank-owned solar systems,” which is certainly a prerequisite for getting financing parties on board. That report also name-checked Tigo’s contract manufacturer, Inventec, as “highly respected” and well-managed in making Tigo’s optimizer units, which are now clipped into existing panels and networked via various means for central monitoring and control.

Second, Tigo announced last week that Germany’s TUV Rheinland Group has certified the Tigo Energy Junction Box -- Tigo’s panel-embedded system -- for sale across Europe and North America. That certification is the fruit of a two-year process with “junction box and module manufacturers executing extensive product testing to ensure high reliability, safety and performance,” and is the first of its kind for the type of “smart module” that Tigo is making.

What’s the next step? Paul Grana, Tigo’s director of marketing, told me that a 2.2-megawatt project unveiled by partner Upsolar in Vermont last month came bundled with Tigo’s electronics, although not fully embedded in the junction box, since the two didn’t yet have the TUV certification in place to do so at the time.

The benefits for Tigo are clear: the more its technology is embedded in partners’ panels, the less work Tigo has to do in the process, leaving sales, certifications, UL testing and the like in the hands of the module makers.

But these same issues could serve as major headaches for solar panel makers, and are likely to retard the progress of panel-embedded solar electronics for some time, GTM Research Solar Analyst MJ Shiao noted.

“From a cost perspective, the embedded product is going to be cheaper,” he said. “But right now, that cost savings isn’t yet worth the risk to the module manufacturers.”

“The question for them is, first of all, is there enough field data out there so I know that these things aren’t going to fail,” he said. “Then there are all these questions about effects on the module’s mechanical reliability,” though those are more pertinent for microinverters, which are heavier and run hotter than Tigo’s power electronics, he noted.

Panel-level optimization or power controls will also have to prove that they’re cost-effective against central inverter architectures, which make up the vast majority of today’s PV systems, Shiao noted.

In general, the decentralized camp says that putting IT at each panel yields much easier design, more flexibility on string sizes and a (slightly) better energy harvest -- as well as reams of data to analyze for some future value. The central control camp say they can organize solar arrays in smaller discrete units of power conversion to avoid the biggest problems with large-scale systems, while avoiding the extra costs of multiplying critical control systems across thousands of panels, rather than a few central devices.

Right now, Tigo’s costs for current projects run about 10 to 25 cents per watt in gross costs, Grana said. That's a figure that's dependent on scale, with lower costs for bigger installations, he said.

That number is not quite to the 5 to 10 cents per watt the company was targeting for 2012, according to previous statements. Still, Grana said the company has a clear pathway to paying off those extra costs across a range of benefits, from improved efficiency and longer panel strings that can reduce costs by 5 to 10 cents per watt, to improved power controls and safety features that add additional value.

Tigo also doesn’t disclose its sales and shipment figures, Grana said. That makes it difficult to compare its market share to DC optimizer competitor SolarEdge, which claimed its millionth shipment in May and is aiming for 2 million sold by year’s end. It also makes it tough to check current figures against Tigo CEO Sam Arditi’s statement in December that the company is planning capacity for more than 4 million units in 2012.

Tigo has raised about $50 million so far, most recently raising an $18 million round in December. One big question is whether or not the company’s DC optimization route offers enough value to make it more worthwhile than microinverters on the smaller scale, or well-designed central systems on a more massive scale.

As for panel makers, they’ll be making their own decisions about Tigo’s pluses and minuses, as they seek to differentiate their products in an increasingly commoditized business. We’ve seen panel makers move increasingly toward linking power electronics, energy storage and other value-adds to their offerings, at the same time as they seek to cut balance-of-system (BOS) costs.