At Synergy, we keep getting questions about the Tesla solar roof, and I wanted to take the time to respond.
The concept of Tesla’s solar roof is GREAT, but because it takes away all the concern of a solar array’s aesthetic versus a traditional roof. However, the actual product does not yet exist beyond the initial concept. In addition, there are many hurdles to making this eventual solution a reality for homeowners.
Tesla’s marketing tells us that these solar shingles will not cost more than a traditional roof. However, they are (in fact) comparing it to a slate or tile roof, which for the average home would run around $60,000-$70,000, and not the standard $12,000 for an asphalt shingled roof.
Even after the existing 26% solar tax credit, it would leave the cost of this solar roof about three times more than the cost of a traditional shingle roof, making it prohibitively expensive for most homeowners. Although the initial costs would eventually be returned in energy savings, especially if you were to spread out the cost of solar across a 30-year mortgage, it is still difficult to wrap one’s head around an additional $35,000 expense on a $300,000 home build.
The second major issue with the Tesla solar roof concept is that no two roof systems are exactly alike. Roofers need to be able to cut and tailor their roofing material on-site to get the perfect fit.
Solar cells have a specific structure that must be adhered to, so cutting them on-site in real-time is not very practical or really even possible with current standard solar panel technology. Although there are some other existing solar options, nothing comes close to the efficiency of today’s standard solar cells.
New Solar Technology
The third concern about Tesla’s solar roof has to do with how the solar cells would capture energy from the sun. Solar energy is captured in DC power, but your house and the utility grid all run in AC power. Traditional solar systems will invert the DC power to usable AC power.
There are two standard ways to invert the DC to AC. The first way is to tie all the panels on the roof together as one and wire everything into one central inverter. The problem with this is that the inverter focuses on the lowest common denominator for its power production, so in a string of 20 solar panels, they all drop to the level of production of the weakest panel.
This is especially an issue on a cloudy day as only one panel in the shade lowers the performance of all the other panels. In an entire roof situation, at least some part of the roof will be shaded all day long, so a central inverter is just NOT practical for a solar roof.
The second most common option to invert the DC power to AC is to have a single inverter on each panel and all panels, individually. This is called a micro-inverter, so there is no loss in power from other panels being shaded. Most of the examples of solar shingles are small one to three square foot panels, which would mean an average-sized roof would need hundreds of panels and hundreds of micro-inverters. This would drive the costs up astronomically, also making this an impractical solution.
Waiting for the Future of Solar Technology
Now I am a huge fan of Elon Musk and all his accomplishments. It is also certainly possible that he has the next game-changing technology that is perfectly suited for his solar roof concept. If he has it, it’s the best-kept secret in the industry.
What is more likely is that the Tesla marketing department has gotten out in front of the engineering department in promoting something that is more concept than reality. If this is the case, Musk is no more guilty than any other major corporation because let’s face it — the marketing departments of most companies are pretty aggressive in blurring the lines between what is and what will be.
As I said in the beginning, I really want a solar roof and I do think we will get there someday! But everything I see coming out of the industry is telling me that we are anywhere from five to seven years away from this being a feasible and comparable option, with some experts predicting 10 years or more for mainstream availability. So…the moral of the story is that if you are interested in solar your best option today is a traditional solar panel array installed by a professional installer.
Elon Musk has made great strides in the last 4 years but the solar roof is still not ready for primetime.
Since my original article Tesla has installed close to 400,000 roofs primarily by Tesla’s actual installers near his factories in California and Nevada. Only being able to buy a roof from Tesla direct has very limited territory they could actually cover and they are just now bringing on roofing and solar contractors in other markets to satisfy the demand. They have been able to lower their initial cost of installation, but still not enough to be competitive with asphalt roofs and traditional solar panels. They are estimating a $50,000 cost for a small roof and complicated roofs like many Lexington homes have would cost well over $100,000. Just not a feasible option when compared to what is available to the consumer and ready to install today.
To resolve the complicated roof concern the Tesla roof is paired with a lot of metal and non-solar glass panels, this allows them to work with just about any roof but areas of the roof that are complicated will not be solar.
They still are working with DC to AC power string inverters, while this may be cost-effective it still causes production loss due to shading so the solar roof tiles have to be a lot less efficient than a traditional solar panel with a smart inverter. In solar pricing, it is common to talk about cost per watt and Tesla has the solar roof down to about $2 per watt but that’s “possible” watts not actual so 360 degrees of the roof would have to be in full sun to count the “possible” watts. A traditional solar panel that’s facing perfect south with a smarter inverter could do the same job with half the size system so comparing cost per watt from a solar roof to traditional solar panels is like comparing apples and watermelons.
Again, I am a huge fan of Elon Musk and to be honest, I am very impressed at the strides they have made in making the solar roof a reality. The truth is they are very close to making it a reality in areas of the country that are mainly more expensive Spanish tile or slate roofs. The Tesla roof stacks up really well against those more expensive roofs but it’s still 1.5 times as expensive as traditional shingles with solar panels. 4 years ago I said Tesla solar roofs were 10 years away from being mainstream at least for our type of construction here in central KY, Musk might beat that timeline but not by much.