The German government is clear in this point: Until 2020 and later on wind will deliver the bulk of the additional energy required. http://www.bundesregierung.de/Webs/Breg/DE/Energiekonzept/ErneuerbareEnergien/erneuerbare-energien.html explains it quite well, although in German. The installation (and renewal) of windgenerators, biomass, photovoltaics, improved insulation of housing, an intelligent grid and pump water storages will produce and deliver the electric energy.

This will require a huge investment, but the investment will be done now, at a time when Germany is doing comparably well. Bottomline is: the conventional sources of energy are finite. So better create the turnaround early than being forced by the circumstances to do it in 20-30 years when conventional energy is getting even more scarce and the cost of tranformation will be much higher. After all it remains to be a technical challenge now that an old policital conflict ended.

Is it achievable? I believe so.

The way how Germany changed energy production in the recent 10 years shows quite clearly what can be done in comparably short time with a combination of opening the grid, fostering competition (like having many instead of just a few energy producing companies), subsidies for investments and a market for electric energy comparable to a stock exchange. A clever mix of regulation and market instruments can induce huge changes at bearable cost for the customers.

To say it in all clarity: Neither coal nor natural gas will be the planned replacement.

Probably there might be the requirement to use fossil fuels for a limited amount of time, but the German government did not only end nuclear power again. This decision resumes and enforces a process of transformation that was already started in 2002 by the Leftist-Green coalition, a move towards Renewables as a major source of energy in Germany.

At least they seemed to have learned from the launch here in Germany. The car was introduced as fun-car for young people, the campaign totally flopped and sales stayed far behind expectations. Nowadays this car seems to be accepted as useful transportation device for a 40+ target group, with a little air of cult. It's a good car for granny: easy to drive, low on consumption and cheap insurance. And some funny advantages like special half-size parking in some cities (e.g. Basel) or legally putting the car at the right angle to the sidewalk to save space. So launching a campaign directed to the usage of it seems the perfectly right way to me. But indeed: considering the size, the mileage is poor and it is a bit too expensive.