The Tesla Solar Roof is here, and if company CEO Elon Musk has his way, there will be one on most houses within 15 years. But despite its energy efficiency and dazzling looks, clean power doesn’t come cheap — and Tesla’s listed price is a little hazy on some of the details. So how much will it actually cost?

Tesla offers one figure for the cost of its proprietary solar roof: $21.85 per square foot, on average. Musk has said the tiles will cost “less than a normal roof.” The problem is Tesla’s messaging and advertising for the roof all factor into 30 years of energy savings from going solar. That makes sense, given three decades is the typical lifetime for a roof, but those aren’t savings a buyer will see on day one, or even day 1,000. And the initial cost is steep.

The Tesla Solar roof looks pretty sweet, in the words of Elon Musk, but how much would one actually cost? Tesla

What’s a Normal Roof?

On Wednesday, the company released a couple amazing photos of the solar roof installed on a house, a visual reminder that Tesla’s tiles combine the beauty of slate and the practicality of solar. They were the first actual houses — not ones on the set of Desperate Housewives — to have Tesla roofs that the public has seen.

While the high-end slate tiles looked amazing, the majority of homes in America use a cheaper asphalt shingle roof. Per Tesla’s own chart below, asphalt shingle roofs cost, on average, about $5 per square foot to install. DIY installations come even cheaper. So right off the bat, Tesla’s pricing puts it more in the range of premium roof materials, like tile, metal, and slate.

Their chart doesn’t actually include the pre-energy savings cost of the solar roof panel. We’ll get back to that.

Calling Some Roofers

Homewyse has an online calculator for a whole host of costs and different installation plans for a shingle roof. Just to give it a shot, I looked at what it would cost to replace the asphalt shingle roof on my family home in the 93651 zip code of California. It’s a single-story house with what I’d estimate is about 1,800 square feet of roof. According to the Homewyse calculator, I’m looking at between $4,900 and $6,200 for a new roof without the cost of taking off the old roof. That breaks down to between $2.71 and $3.46 per square foot.

Homewyse includes some significant costs that Fresno Roofing didn't. Homewyse

Homewyse is careful to note that these estimates are not official quotes by professionals. So I called up the Fresno Roofing Company, a local business near my hometown in the hills outside Fresno. Lorn Thompson, an employee there, told me that for an 1,800-square-foot roof, I was looking at about 19 to 20 “squares,” which roofers use as a unit that describes a 10 foot by 10 foot chunk of roof (100 square feet). For materials alone, I was looking at $75 to $85 per square.

Thompson yelled to Ricky, Fresno Roofing’s field director, for a quick quote on how much that would cost to be installed: Ricky says it’s about $30 per square. Totaling up materials and labor, it comes to $2,300 for a new roof ($1.28 per square foot) — significantly lower than Homewyse’s estimate, which included a bunch of supplementary costs as well. Again, that number’s going to be low, because it’s not figuring in the cost of taking off the old roof, if necessary. Tesla’s price estimate does already include the price of removing the old roof.

What’s a Tesla Solar Roof Actually Going to Cost?

Here’s where it gets tricky. Tesla has a cost calculator on its website which looks at a home’s location, size, and power demands and offers a quote for how much it’s going to cost. The big factor, it seems, is how much of your roof needs to be solar. Something that isn’t readily apparent about Tesla’s roof tiles is that they’re not all solar. In fact, the company estimates that the average house will only need, or be able to accommodate, about 40 percent of the solar tiles — the rest will be identical looking but non-solar glass shingles. A non-solar tile costs $11 per square foot, but the solar-paneled ones are $42 per square foot.

I decided to try it for the same house: foothills of California, 1,800 square foot roof, 40 percent solar tiles.

Wait, what? Tesla

Hold up, my solar roof is going to pay me money? That right there is the big sell. The final number on Tesla’s site is how much money a solar roof is going to make you over 30 years, which is the standard warranty for an asphalt shingle roof. Tesla’s warranty is “infinite,” Musk says. The numbers that aren’t so apparent, however, are the actual costs.

The calculations above show me that, including installation and materials and everything, the solar roof is going to cost me $52,100. Add in a Powerwall battery, which is necessary for the roof setup to work, and that’s an extra $7,000 to $59,100 right out of pocket. Part of Tesla’s selling point is the generous tax credits — until 2019, homeowners can deduct a full 30 percent of their purchase and installation costs for solar energy from their taxes. After 2019, it goes down to 26 percent; after 2020, 22 percent; and after 2021, it’s zero for residential systems and 10 percent for commercial. Congress could extend those tax credits — they previously did so in 2015 — but for now the pressure is on the consumer to go solar ASAP.

A bird's-eye view of the solar roof Tesla

Let’s break that $59,100 quote down a bit. For my family home, at 1,800 square feet, that works out to $32.83 per square foot. Yes, that’s before tax credits, and it includes the Powerwall — but unless Tesla’s customer base is entirely people who own Tesla vehicles and thus already have those $7,000 batteries installed, and unless they all buy before 2022, all those costs will have to be figured in.

At the TED 2017 conference in April, Elon Musk estimated that it would be unusual to see non-solar roofs as soon as 15 years from now. He may be right, and his technology is certainly on the cutting edge. But his time estimate here, like many of his predictions, is incredibly ambitious. Unless Tesla solar roofs can compete with the upfront cost of an asphalt roof, or get close, it’s going to be hard for people to switch — not because they don’t want to, but because they just can’t afford it. Tesla says it hopes to start offering financing later this year, but for now those who can’t afford $60,000 up front will have to look into getting a loan. That’s a big financial commitment to take on when an asphalt shingle roof could cost a fraction of that price.

It’s worth noting that Musk’s general business plan has always been a gradual, incremental move toward making its products affordable for everyone. Take Tesla’s electric cars: first the hyper-expensive Tesla Roadster, then the luxury Model S and Model X, then the mid-range Model 3, and, eventually, maybe a budget option.

For now, customers that do have the purchasing power for a premium roof have another excellent option for making their house as green as possible. Those initial purchases may help bring costs down so that 15 years from now, solar roofs are in a place to make Musk’s predictions come true.