So, the Sun shines on Earth and in that sunshine there is energy. Plants convert that energy into mass because energy is mass. E = mc2. Energy equals Mass times a constant (which is not important here). We eat the plants for energy, or we eat animals that eat the plants. That’s how we survive.
Well, solar panels are humans’ attempt at making “plants” that convert the Sun’s energy into energy we use – to heat, chill, or light our homes, to power our TV’s, fridges, computers, etc. Well, it’s not easy converting that sunshine into energy we can use. And as it turns out, most solar panels convert 12-15% of the Sun’s energy that falls on the panel. The Sun dumps ~1,000 W/m2 at sea level on a clear day (source: wikipedia).
Panel ratings are standardized – measured under standard testing conditions (STC). A panel that is 17.24% efficient, was not manufactured to produce 1,000 Watts. It was manufactured to produce as much energy as it could, and ended up converting 17.24% of the sunshine.
So basically an independent rating company will shine 1,000 W/m2 at a certain temperature (25 C) and air mass (AM1.5), and measure how many watts the panel will output. If it outputs 200W and the module is exactly 1 m2 in area, then it’s efficiency would be 20%. However, most modules are greater than 1 m2.
Sanyo VBH235SA06 rated at 235W has a module efficiency of 18.64% and it’s area is 1.26 m2.
So: (1,000 W/m2 * 0.1864 * 1.26 m2) = 234.86 W…. or 235 Watts.
Or: 234.86 W / (1,000 W/m2 * 1.26 m2) = 18.64%
…meaning that this particular panel outputs 18.64% of the energy that the Sun dumps on it (which ultimately varies by day, time, location, temperature, etc). If you’re at sea level, at noon, it’s 25 degrees Celsius outside, the airmass is AM1.5, and you have no losses due to wiring, shading, or anything, then this solar panel should output almost exactly 235 Watts.
So, should you wait for solar panels to convert 80% of the Sun’s energy? Absolutely not! You should install solar panels as soon as possible so that humans can continue to live, because chances are that the energy you’re using in your home is coming from a source that will disappear long before the Sun and probably polluting Earth (killing you) much more so than the Sun.
Go solar. It’s good for your health.