I would say it really depends on the PNG compression library you are using.
Tools like RIOT or Compressor.io can give you optimal results on PNG compression.
See my reply below.
According to VOX article, "installed" means 2x of money/watt value. So, according to Bloomberg article, if First Solar panel is 40 cents/watt and Trina panel is 45 (40+15%), installed should be 90 (45x2). But then again, according to VOX, 3$ per watt is far away from 90¢.
In my opinion, even taking in account the cost of installation, the values expressed in the two articles are completely different.
dollars/cents per watt should be a standard measure. Plus, the VOX article states that "...we'd also likely need to rethink how we install solar panels. After all, the panel itself is only half the cost.".
Right now there are 2 different articles on Hacker News front page stating the opposite (almost).
Bloomberg article (http://www.bloomberg.com/news/articles/2016-04-14/first-sola...) states the following: "First Solar is producing panels for as little as 40 cents a watt, or about 15 percent less than China’s Trina Solar Ltd. In 2019, First Solar’s module cost could be as low as 25 cents a watt, according to analysts’ models.".
VOX article (http://www.vox.com/2016/4/18/11415510/solar-power-costs-inno...) states the following: "How cheap? Sivaram and Kann argue that the industry should set a goal of pushing the installed price of solar to 25 cents per watt by 2050 — down from around $3 per watt today."
Right now there are 2 different articles on Hacker News front page stating the opposite (almost).
Bloomberg article (http://www.bloomberg.com/news/articles/2016-04-14/first-sola...) states the following: "First Solar is producing panels for as little as 40 cents a watt, or about 15 percent less than China’s Trina Solar Ltd. In 2019, First Solar’s module cost could be as low as 25 cents a watt, according to analysts’ models.".
VOX article (http://www.vox.com/2016/4/18/11415510/solar-power-costs-inno...) states the following: "How cheap? Sivaram and Kann argue that the industry should set a goal of pushing the installed price of solar to 25 cents per watt by 2050 — down from around $3 per watt today."