It’s been about a month since Tesla Motors CEO Elon Musk first announced the development of a solar roof tile unlike anything currently on the market, but it’s still anyone’s guess as to when they will actually be available, exactly how much they will cost, and how much electricity they will be able to produce.

The tiles are made of textured glass, and when viewed at an oblique angle from the ground they look exactly like roofing slate or terracotta tile. (They also will be available in two other glass finishes.) From directly above, the tiles act like any other solar panel and admit sunlight that generates electricity.

What Musk describes as a “hydrographic coloring” process — combined with micro-louvers in the film that work like a privacy screen on a computer — allows the tiles to mimic the look of another material, according to a story posted at Forbes. A roof capable of generating power without the visual distraction of the modules and racks of a typical solar array is intriguing on its own, but Musk now promises the shingles would cost less to manufacture and install than a “normal” roof, Bloomberg reported. The electricity, he said, “is just a bonus.”

The tiles would be integrated with Tesla’s Powerwall battery and, the company no doubt hopes, an electric vehicle in the garage.

Those, at least, are the bare bones of the Tesla/SolarCity vision of the future. Yet the company isn’t sharing many additional details. A recent email asking for more information got this reply from the Tesla media office: “Due to the number of media requests we receive on a daily basis, we are not going to be able to provide you with specific answers to your questions.” Instead, the company referred to a press kit that talks about the shingles only in very general terms.

Extrapolating from what’s known

Fortune said that 3M developed a new solar film specifically for the Tesla solar shingles after Tesla approached the company with the concept. Tesla will apparently team with Panasonic to work on the technology at SolarCity’s giant factory now under construction in Buffalo, New York.

How the shingles will be installed, and how much power they will be capable of producing, are two key questions that will face installers and homeowners. Barry Cinnamon, CEO of Spice Solar, has spent some time thinking about those questions and summed up his best guess in a recent blog posted at Greentech Media.

Cinnamon estimates that each shingle will produce 6 watts of electricity, so a rooftop with a rated capacity of 6 kilowatts would need about 1,000 shingles.

Because wiring 1,000 shingles individually would result in 2,000 wire connections, an installation and maintenance nightmare, Cinnamon guesses that Tesla is more likely to make 24-shingle bundles that could be installed as a single unit, reducing the number of wire connections dramatically.

Cinnamon based his cost and payback estimates on early statements from Tesla, which have since been lowered. He predicted a simple payback on a new production home with a Tesla solar roof of 8.2 years, compared with a 6.5-year payback for a conventional photovoltaic (PV) system. Making the shingles cheaper would only make the equation more attractive.

“Innovations in the business model related to solar roof installations, for which both Tesla and SolarCity are well known, can further reduce costs,” Cinnamon wrote. “So on the whole, I’m optimistic that new solar technologies like Tesla’s solar roof will contribute to continued rapid growth in the residential solar industry.”

Installers may need some convincing

The exact cost of a Tesla roof is still a mystery. Musk says that the solar tiles won’t cost any more than a normal roof, but what’s “normal” — three-tab asphalt shingles, or slate that costs $1,600 a square? Those and other uncertainties are good grounds for healthy skepticism, says Phil Coupe, co-founder of Revision Energy, a Maine-based solar company that’s installed 6,000 solar projects in the last dozen years.

“We don’t want to be a wet blanket on the whole affair but we’re waiting to be convinced this is a game-changing product as opposed to another really excellent marketing hook from Tesla/SolarCity that gets their name in print but doesn’t actually do a whole lot for fossil fuel consumption and greenhouse gas emissions,” Coupe said in an interview.

“Right now we are a little bit skeptical,” he said. “Elon Musk has done a great job of marketing products that are not yet available for consumption and generating a lot of buzz for things that people can’t actually have. And so with the solar roof tiles, we are needing to be convinced this may be some type of viable new technology.”

An underlying premise of the Tesla solar shingle is that people would rather not look at a conventional solar array. Why else invest the money in a solar roof that looks like something else?

Coupe, however, says very few of his customers seem bothered by the look of conventional solar arrays, and when appearance looks like a deal-breaker there are already alternatives on the market.

“For a tiny subset of our clients, aesthetics are the overarching concern, and that small fraction of clients occasionally results in us not getting a project on the roof,” he said. “But the great news now is that we have community solar farms available for people for whom aesthetics is really a primary concern. They can buy a share of panels that live in a field somewhere remote from their property, and they have the power from that solar farm dedicated to their meter. They get all the benefits of solar ownership, they just don’t have the solar array on their own property.”

Will potential customers hit the pause button?

Coupe wonders about one other possibility: will the prospect of cheap building-integrated photovoltaics down the road make potential customers delay a decision to buy?

“When SolarCity/Tesla comes out and announces a new product that may not be ready for one to three years, it can be kind of a setback for existing companies because it might cause customers to pause and wait on a solar investment,” Coupe said. “We see good reason for urgency around the idea of reducing fossil fuel consumption and greenhouse gas emissions, so a product announcement talking about a product that’s still in the lab and not ready for consumers can unnecessarily delay people’s investment in a clean energy solution.

“We really don’t think that’s awesome for the industry, nor for the urgency around this issue of 7 billion people burning fossil fuels in a closed atmosphere.”

Another question: Will Tesla make the solar tiles available to installers like Revision Energy, or market them only through SolarCity?

“I have not the slightest idea,” Coupe says. “The good news about the Powerwall is that it is available to other installers, and so we’d like to imagine the product will be available for everyone, but it’s not determined at this point.”