Tesla’s Solar Roof – A Cost Analysis

I’m sure blitheringly idiotic legislators in California are salivating over Elon Musk’s home solar . OK, so this sounds more like blog than a cost analysis. Then again, I’m a cost analyst, so perhaps it is a cost analysis, and perhaps a bunch of rich fat cats in the land of fruits and nuts are looking forward forking over tons of money for a sexy roof. Either way, I’m forging ahead, because YOU, the homeowner who still can’t make heads or tails of their options, deserve to have something to which you can compare.

And compare we shall, with these three options:

  1. Tesla’s Solar Roof: 9.45 kW system on a 1,862 square foot roof; $64634 for the solar roof, $10,050 for the Powerwall (storage and grid tie-in), and another $10,630 for roof and site repairs. Total: $85,314, or $35 per square foot of roofing.
  2. Wholesale Solar’s Do-It-Yourself solar panel system: A calculated 6.34 kW system, storage, and grid tie-in for $13,310 to $16,637.
  3. A regional quote which I could not obtain without giving away my life’s history. Same dud with two national installers.

Article: “Tesla’s Solar Roof is incredibly sleek… and incredibly expensive

Most of us could care less about paying a $34,000 premium for a “sleek, sexy roof” particularly when a DIY solar roof with comparable performance and both storage and grid-tie costs less than $17,000. The cost of qualified labor might run you $10,000 to $20,000, but since it is a DIY and you like DIY projects, you can have fun while saving $68,000 on this year’s summer project.

Yes, a QUALITY DIY solar system with storage, grid tie-in, and the same output specs as the one mentioned in the article costs between $13,310-$16,637. I rounded it up to $17,000, as that’s exactly one-fifth of Elon Musk’s $85,000 roof. If you don’t want to do-it-yourself, the labor cost will run you $10,000 to $20,000.

All DIY values were sourced from Wholesale Solar’s Panel Cost Calculator using their Grid-Tie Solar+ Energy Storage option, Colorado Springs as the location, 943 kWh average monthly energy consumption (almost the same as the 945 kWh used in the article’s example), 13 cents per kilowatt-hour, 100% power bill offset, and while claiming the 30% Federal Tax Credit. Their calculations resulted in a 6.34 kW system size and an estimated lifetime utility savings of $44,125.

Why pay $85,000 for a “sleek roof” when you can have a rock-solid PROFESSIONAL system installed for just $27,000 to $37,000? Or better yet, have some fun and skin some knuckles and save those labor costs.

This is not Elon Musk’s attempt to help solve energy problems. This is priced solely to put massive funds into Elon Musk’s pocket. He has Bezos envy and can’t stand it, and is certainly calculating on being the primary installer in California, whose legislators have mandated all new home construction include solar panels to provide at least

FURTHERMORE, the payback of the $17,000 system is 8-9 years. There is NO payback for Musk’s system because the calculated payback period of 42.5 years exceeds the life expectancy of the roof by at least 50%. Unless, of course, Elon Musk has *SOMEHOW* figured out how to extend the life of solar cells considerably.

Solar cells degrade about 1% per year during the first couple of decades, so by the end of the typical 20-year warranty, they’re producing roughly 80% of original output. But it’s not linear, and after then other problems develop, so by 30 years, you’re looking at 60% output but may have to change out your grid tie-in. Your storage system, being batteries, are almost certainly going to have to be replaced prior to the 15-year mark.

In short: NO DEAL. Certainly not at $85k when I can have a system with matching capabilities installed for $25k.

Don’t get me wrong — I’m NOT bashing solar! I am, however, bashing Musk’s 5x over-priced system, or 3x if you account for part of the cost be accounted for by the fact that it is indeed a very sleek-looking roof.

If you can afford the extra $34,000 for sheer aesthetics, go for it, but even then it’s still 3x overpriced.

EXCEPT… for the fact that it includes a roof. Remember, Tesla’s solar roof negates the need for roofing. In order to perform a proper cost analysis, we need to consider the cost of roofing. Unless you like burying an expensive roof beneath expensive solar panels, perhaps solar roofs really are a better way to go. However, solar panels are already wind, rain, and hail proof, and with very small modification they could technically replace shingles without doubling or tripling the cost of your solar panel installation, as Tesla wants to do.

AND… for the fact that ” Research conducted by the Appraisal Journal states that a solar electric system may increase your home’s value by 20 dollars for every 1 dollar in annual utility bill savings.” (Source) Thus, if your decision to date was based on your electricity cost savings alone, you’re short-changing yourself and your heirs.

In order to proceed, we need more data! Let’s start with the average national cost to install or replace various types of roofs, courtesy of Homeowner.com’s Select Your Roofing Project:

  • Metal: $8,541
  • Tile: $12,474
  • Asphalt Shingle: $6,672

Clearly, shingles are the cheapest roofing material, initially, but as most homeowners already know, they must be replaced on a regular basis, perhaps every 7 to 20 years, depending primarily upon weather and heat conditions.

Metal roofs are about 50% more expensive, but they last for decades. They’re noisy as could be when it rains, though.

If you’re living in a location where tornadoes and hail are very rare, such as the Southwest United States, then tile roofs make sense. I knew a gentleman in Las Vegas whose tile roof was built in the 1950s. As of about 2002, 100% of his shingles remained intact, as did the wood rafters and sheeting holding them up. The wood was sagging a bit, and he was considering replacing the rafters and sheeting, but would simply re-use the tiles. While stationed in Iraq, I’d often come across pottery relatively large shards of pottery dating back more than 4,000 years. If fired clay can withstand the shifting sands of the desert for more than 4,000 years, it’s probably more sturdy than you realize.

The other part about roofs involves pitch. Nearly all home roofs in the U.S. are pitched in order to allow for water runoff. In areas where it snows, building codes require a minimum pitch in order to keep too much snow from piling up before sheeting off. It’s extremely rare to find a single-slope roof. Most roofs are build with a centerline ridge running the length of each major floorplan, and towards the sides of the house. Gables have their own ridges, often slightly lower than the main ridge. More modern roofs have hip ends instead of gables, relying instead on the superior insulation to keep the home below cool rather than gable vents. In sunnier climates, however, such roofs can become very hot, minimizing the life of asphalt shingles. Tiles and metal, however, don’t care about the heat.

A roof’s pitch, however, limits northern slopes from being effectively used for solar power.

Throughout the year, the sun’s position swings from 23.4 deg north of the equator (Tropic of Cancer) during the Summer Solstice in June, to 23.4 deg south of the equator (Tropic of Capricorn) during the Winter Solstice in December. Key West, the southern-most point in the continental United States sits at about 24.56 degrees, so even during the Summer Solstice, the sun never gets to be fully overhead.

When you crunch the numbers, the ideal for all locations is a solar panel facing due south. The angle of tilt depends on the roof pitch, but throughout most of the U.S., and solar panel tilt of about 30 degrees works well, and that’s close to the pitch of most roofs.

What’s clear, however, is that north-facing pitches don’t receive enough sunlight even in the summer months to be worth the expense of using any solar panels at all. For east and west-facing pitches, it’s a draw. If that’s all you have, then use them. Otherwise, you’re better off using solar on your most southern-facing pitch and not worrying about the rest. It might not provide you with all your energy needs, but you won’t be wasting tens of thousands of dollars, either.

Having said that, for homes in the tropics i.e. between about 20 deg north and south latitude, it’s worth it to apply solar panels over the entire roof.

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