Australian and American roofing can be quite different, with variable build methods, regulations and environment – such as snow. But it's a good place to start. Keep in mind that Tesla is targeting high end roof tiles, not the budget variety or steel roofing.
$US21.85 US per square foot equates to $US235 per square metre, or $318 per square metre at current exchange rates to the Australian dollar.
Tesla suggests that at the $US21.85 US price, the ongoing solar generation over 30 years makes the roof cost competitive with a normal roof.
Pricing depends on a huge number of factors, but an average roof in Australia, fully installed, ranges from about $80 a square metre on the low end, to $130 a square metre for higher end products such as terracotta tiles.
Still, Tesla is targeting the higher end, so let's use the $130 a square metre figure. That means the Tesla solar roof is about 2.5 times more expensive than a comparable — but not solar — roof.
Using a large single Australian home as an example, it could have a 300-square metre roof — similar sizes are used for the Tesla price example. That's $39,000 worth to replace with a normal roof, or $95,400 if installing a Tesla Solar roof. That means the Tesla roof is $56,400 more expensive.
So 35 per cent solar on a large Australian home with a 300 square metre roof is about equivalent to a 10 kW solar array. According to Solar Choice, that will net us at least 40 kWh or so a day, depending on location. Solar output drops over time, but the house should generate 400,000 kWh or so over its life.
That means that each kWh produced needs to be sold for, or save the household, about $0.14 per kWh for the cost to break even. Houses with high direct solar use might achieve the savings, but it's well above the $0.08 or so per kWh from feed-in credits.
An array to generate the same 10 kWh as the example Tesla roof above costs an average of $14,675 in Australia, according to Solar Choice. Darwin actually bumps that average up a lot, so $14,000 is closer for most of us.
So a normal roof plus normal solar on the example home from above costs about $53,000, versus the $95,000 for the Tesla roof. That means the Tesla Solar Roof isn't double the cost, but is a lot more expensive for the same solar capabilities.
As a comparison, over a 25-year life (Australian solar panels typically have a shorter warranty), the solar panels should make at least 333,000 kWh. That gives a break even saved cost per kWh of about $0.04 – half most grid feed ins.
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