The Preservation of a Healthful Environment: Solar Roof Series – Part 4

Yep, I’m going to cover the Tesla SolarCity panels.  I left this one to last because unlike the “roof plus array”, Tesla offers shingles that turn the entire roof into a collector.  Aesthetically, they look like metal or stone coasted shingles.  Price wise, they are much more expensive.  The interesting part is that with design, not only does the entire roof become an array, but all costs are subject to ITC, not just the array portion of “roof plus array”.  They use HIT technology (from Part 2) and have plants in Fremont, CA and Buffalo, NY.  Both cities utilized tax policy to land the plants which generated a couple of thousand jobs.  Someday I’ll write something on the symbiotic relationship between government and technology in the sustainability area.

This series has covered a lot of ground including a roof primer, engineering background and governmental perspectives.  This installment will finally get around to addressing my original reason for posting; the Tesla SolarCity pricing announcement.  I wanted to explore the economic viability of the roofing system.  Would this be a practical alternative today, or something to wait for?

SolarCity tiles are more attractive than solar panels.  There are four styles planned, two of which are already being produced:

  • Tuscan
  • Slate
  • Smooth (planned)
  • Textured (planned)

Production is currently being handled by a facility in Fremont, CA, but a new facility in Buffalo, NY should come online soon.  I grew up in Buffalo and returned for a visit last month.  I saw the SolarCity plant and it is indeed impressive.  In my opinion, it is a good example of government and industry working together because it is not based on tax incentives alone.  The state owns the facility and equipment.  Tesla will use the facility and hire the workers. Jobs and innovation; a developing relationship.

Since this series began a couple of weeks ago, Tesla has installed its first SolarCity roofing system. Bloomberg reports that the cost of SolarCity tiles are $420 per square and they compared this cost to standard roofing with a separate solar array, the common configuration.  They also identified three target markets:

  • Terra Cotta (or Tile)
  • Slate
  • Glass

They used the same comparison approach we used in this series; roof and array versus SolarCity.

There is no methodology information provided in the Bloomberg article, but they came up with the same conclusion.  Using the cost figures from our first post and adding in the effect of the 30% ITC program, it is clear that one of the economic advantages of SolarCity is the entire roof is subject to ITC.  ITC has a big effect on the economics as shown by the red line on the following chart.

Our analysis shows the competitive market for SolarCity to be:

  • Copper or Zinc
  • Tile (Terra Cotta)
  • Metal Seam
  • Slate

It is difficult to predict the effect that high volume production and sponsored incentives will have on the consumer costs. On the performance side, we will know very shortly how these tiles perform.  The move to Panasonic HIT technology may have delayed production in Buffalo, but is clearly a shift that will benefit consumers.

Before I end, please checkout the excellent work being done by Google’s Sunroof project.  You should lookup your address to ensure that the property you are considering for solar can be positioned in a way to take advantage of sunlight.  It can even help you locate the sunniest places on your roof! And stay tuned for more solar news, as the field is innovating all the time.

The Preservation of a Healthful Environment: Solar Roof Series – Part 1

This is the first post in a series about rooftop solar technology. I was inspired to write this after talking to some members from Hawaii and reading the Tesla SolarCity pricing announcement. The series will cover roofing jargon, costs, underlying technology, legislative policy, regulatory issues and design, so let’s get started.

The growing interest in solar generation in 2016 has been borne out by recent numbers. In May, the UK announced that solar generation has surpassed nuclear and coal generation. Focusing on the US, you can compare state-by-state solar activity using information published by National Renewable Energy Laboratory (NREL) through their Open PV Project. NREL’s SunShot report is an excellent periodical that presents a global perspective. It shows that the US installed the second highest number of solar units in 2016 behind China. This moved the US up to fourth in total installed capacity. Only China, Japan and Germany has more installed solar energy systems. With one more year like 2016, the US will surpass Japan and Germany for installed capacity. Most experts underestimated the performance of US solar in 2016 because of the potential expiration of the Investment Tax Credits (ITC). A future post will be dedicated to legislative and regulatory issues behind solar energy.

Before we can talk more about solar on the rooftop, we should review the rooftop itself. The most common solar setup involves attaching panels to the roof, getting them to point as directly towards the sun as possible, and storing the generated electricity. Some of the more common roofing materials, arranged roughly in cheapest to most expensive order, are:

  • Foam, Spray Polyurethane Foam (SPF)
  • Basic Asphalt (25 year)
  • Architectural Asphalt Shingle (30 year)
  • Fiberglass Shingle
  • Corrugated Metal Sheet
  • Premium Asphalt Shingle (50 year)
  • Built Up Roof (BUR) or Tar and Gravel
  • Metal Shingle
  • Stone Coated Metal Shingle
  • Wood Shingle
  • Shake Shingle
  • Slate
  • Metal Seam
  • Tile
  • Copper or Zinc

Not every roof can use these materials. For instance, on flat roofs, you might go with SPF or BUR, but these materials would not be ideal for sloped roofs. You would typically find BUR and SPF on commercial and urban multi-units. All of the others you find on sloped roofs. I have never seen a tar covered sloped roof.

Each method has distinctive installation procedures, and costs vary significantly by geographic location. Chimneys, dormers and other features of the roof design that require fitting of the material to the roof complicate installation and drive up costs. Higher grade shingles cost more (although the difference in cost might not be as high as you think), and even the underlayment varies based on what kinds of shingles are used.

The jargon used by most contractors is unfamiliar to consumers. Consumers think of everything in terms of cost per square foot ($/SQFT). Contractors use the term “squares” for their calculations where one “square” is ten feet by ten feet or 100 SQFT. This simplifies ordering because the materials are organized on pallets, accounts for waste (unused material) and for any mistakes. I had my own roof upgraded nine years ago and I still have a stack of shingles in the shed.

 

 

The chart above presents the relative cost differences between different roofing materials. Please use this chart knowing that I have accounted for a typical installation that included removing and disposing of the current roof, all material, labor and incidental costs. There are also regional variations that are difficult to capture, which is another reason these are relative costs. These costs are expressed as “squares”, the common unit that will be used in this series.

The red line on the chart signifies what could be called ultra-high end roofing. This line will become important in later posts, especially when talking about the Tesla SolarCity roofs. Here are a couple of interesting things to notice when looking at total installed cost. From left to right:

  • Although the Fiberglass Shingle material cost is less expensive than 30 Year Asphalt, the final installed costs are very close.
  • Shake Shingle and Wood Shingles are nearly identical in material cost, but Shake Shingles take more time to install because they are irregularly shaped.
  • Copper and Zinc material costs vary all of the time, so they were very difficult to normalize

It is important to consider the entire roof when looking at the economics of solar, especially when considering new approaches such as the Tesla SolarCity roof. You don’t attach anything to a Tesla roof, because the roof is the solar collector. When we get to the economics part of this series, we will evaluate the cost of the roof so that we are comparing apples to apples.

The next post will address the technologies behind solar energy collection. The science has improved greatly over the last couple of years. I found the subject matter interesting, but I am an engineer.