a reply to: TheScale
just type in "pv panel energy myths" and you´ll find many calculations but be aware, there are many "pro pv" sites that are as bad as the "anti pv"
fraction when it comes to disinformation.
In my region, you go to the bank, get a credit and you´re set up because they know PV pays back. Even now with prices at 50c/Wp module and payback as
low as 6-7€c/kWh It was more profitable 6 years and more ago, that´s right. Without the subsidizing, the pay you get from the energy companies
would be way less and not profitable, you better use that energy for yourself, if you pay more then you get for the energy. In my case, I get about
double the price for the energy I give to the grid.
So until my contract runs out, it would be idiotic financally to use my own energy. But in reality, the generated energy goes through my "upload"
meter and right back into my "download" meter, to my appliances.
Here are some definitions, it´s important to seperate and know these terms:
energy is the amount of work a physical system is capable of performing. Energy can´t be destroyed or consumed, it´s transfered from one medium and
state to another.
You always pay for the energy. That means, everything you buy, regardless if it´s an apple, a wooden shelf or a pv system. The main cost is already
the energy needed for the resources and amount of work to get them, included in the price. The difference is, there are mixed energy sources and
countries with different energy-costs. Be aware, I use the term "energy" and the term "power".
..is not the same as energy. Power is energy transfer per unit of time.
term: "energy resource payback"
That´s why the energy payback (resource wise) is already payed with the price of the panel. For one module to harvest the energy needed in production
(including resources, until the point it leaves the factory) it takes around 3 years, most times even less.
term: "panel cost payback"
For your panel to payback financially it depends on the price you get for your energy of course and if there are setbacks like panels failures.
term: "panel power (300Wp)"
Wp = Watt peak, that means it´s the absolute maximum amount of power harvested at any given time. So on a very sunny day, with clear air, in the
cold, with optimum angle and orientation, clean surface, no dirt, this panel will output 300W per hour of sunshine.
term: "panel efficiency"
is currently around 18-19% on a 1000W/m² base at a sunny day. I know it was just a crude example from you but 100% is impossible even in space. There
can´t be 90% efficient panels inside the atmosphere. Although, the 1000W/m² do not include scattered light. Some types of materials are better with
difuse and scattered/reflected light. Those are the laminated panels (use cadmium tellerite) and often seen in a brownish color on your calculator.
They work very well lower light conditions.