Three years in, Tesla is beginning to publicly acknowledge the difficulties involved in creating and scaling a solar roof tile.

The electric car company turned clean energy provider has tended to downplay or ignore the long history of failures and disappointments in the solar roof industry. In October 2016, Tesla pitched the tiles as an aethetically stunning tool for a renewably powered future.

CEO Elon Musk is still envisioning a better future, but he's now sharing more of the shortcomings Tesla has encountered in its product development so far. That started with revealing, in a quarterly earnings call this week, that the first two versions of the solar roof were not ready for the big time.

He promised to reveal the third generation the following afternoon. On the following afternoon, he tweeted that the unveiling would take place the next day at 2 p.m. "California time." The next day, at 2:30 Pacific, Musk followed through on his promise.

The third version of the solar roof reflected continued refinements rather than a clear transformation from the previous versions, which were never widely released.

Tesla engineers have increased the size and power density of each tile and reduced the number of parts by more than half. The designers also improved the edges of the roof, which Musk said previously required "artisanal" and time-consuming labor onsite.

Other aspects of the new product still remain fuzzy.

8-hour installation time?

The solar roof will cost less than the combined cost of your average roof plus solar panel installation, Musk said. That's the same promise he made when launching it the first time, three years ago.

"It’s been quite hard to get to this point," he noted. For one thing, he said, roofs have to last a long time, and the wiring has to be safe and not cause risk to the house (Tesla has recently run into troubles with installations catching fire). These observations reflect the challenges inherent to the task at hand, but it was new to hear Musk address the reasons for delayed product arrival.

In another shift, Musk said Tesla is open to working with roofers outside of his organization. A major risk for Tesla's solar roof was its go-it-alone mentality, which would force the company to stand up an entire roofing business internally, and compete against established roofing channels.

Tesla does not have roofing installation partners yet, but Musk said he's open to creating a "Tesla-certified installer" program, and enlisting outside roofers to help improve the installation process. That move could get the product to market more rapidly; it eliminates a potential labor bottleneck and leverages the sales capabilities of established companies. According to numbers through April, Tesla had installed just 31 roofs in California, the leading state for residential solar installations.

The in-house installers are targeting an entire roof installation in eight hours, which would be seriously speedy.

When asked when the roof would be available at mass-scale, Musk replied, "That’s now, actually." But then he noted that anyone can place an order now, whereas actual production was still ramping up. He wants to get to 1,000 per week at some point in the near future.

"The demand will be far in excess of supply," he said, raising questions about wait times for delivery.

The French slate and Tuscan clay roof tiles that Musk showed off three years ago still don't exist as real products. The website now offers two solar roofs: a textured black glass shingle and a normal roof with normal solar panels. A 2,000 square-foot roof producing 10 kilowatts solar power — which is larger than a typical residential installation in the U.S. — would cost $33,950 for the glass tile, or $34,550 for the basic roof and panel combo, the company estimates.

Tesla has not revealed the efficiency of the tiles' solar production, as other companies in the space have done. There will be some loss of efficiency to have better aesthetics, Musk admitted, but he aims to keep the loss below 10 percent. On the plus side, the tiles can fit more solar cells on a rooftop than solar panels could, which could make up for the efficiency loss.

The last big question mark is how much product the Buffalo factory, where Tesla is manufacturing the solar roof, will be able to produce. Musk praised the factory staff's hard work on the project.

"They've really been putting in a huge effort to ramp up production of the solar glass roof," he said. "We’ll definitely make New York proud about that factory."

Setting aside pride, Tesla owes New York 1,460 jobs in Buffalo as a condition of state assistance received in setting up the factory. In May, the company reported it met its 2019 target and had plans for "diversifying its presence" in Buffalo; adding employees working on its other, more developed products such as energy storage and its EV Supercharger.