In Germany I'm not sure that you increase the amount of green energy that get produced by making a choice to be on a plan that "uses" green energy. The German energy market isn't free in the sense that you can raise demand for green energy to raise supply of green energy.
We have laws that everyone who wants to sell green energy into the market gets a gurantee that the energy is brought for a decent price.
You can do so, but it takes market knowledge to find such a plan. There are several plans that offer 100% renewable energy, usually certified in some way (example: http://www.tuev-nord.de/cps/rde/xbcr/SID-7251F8DB-F18E650D/tng_de/kriterienkatalog-oekostrom.pdf). The certified electricity is usually from hydroelectric power plants which are already 100% depreciated and don't get any surplus from the renewable energy levy.
However, there are some plans (for example http://www.gruenerstromlabel.de/english/) that come at a higher price, but also pay for install...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.