Ed. note: This piece first appeared on Energy Outlook, Geoffrey Styles’ blog.

Since I've been taking potshots at German energy policy recently, I was pleased to see that it appears the country's government is nearing a reasonable compromise concerning nuclear power, which accounts for 22% of the electricity generated in Germany. The Financial Times reported yesterday that the CDU/FDP coalition is likely to propose extending the life of the country's reactors by 12-15 years, in order to give renewable energy sources more time to ramp up. Yet while the extension makes enormous sense from the perspective of emissions and energy security, I'm puzzled by the plan's implicit assumption that nuclear power is valuable only as a bridge to more renewable energy, rather than as a key part of any future, low-emission energy mix.

In 2007 Germany's 17 reactors generated 140 billion kWh of electricity. By comparison, all renewable sources amounted to just over 100 billion kWh, with only 3 billion of that coming from the country's highly-subsidized solar photovoltaic (PV) installations. All of these reactors will reach the limits of the their currently-allowed 30-year service lifetimes by 2020, when they are required by existing law to be shut down, and all have provisional shutdown dates within the next few years. The problem is that the incremental growth in renewable electricity required to replace all of these plants does not seem feasible within that timeframe, despite its impressive expansion so far.

Replacing just the net output of those reactors would require total renewable generation to expand by roughly 150%, though much of that expansion would by necessity depend on a much smaller fraction of the renewable power base. Wind currently supplies 6.5% of generation and continues to grow steadily. PV capacity has more than doubled since 2007, from 4,000 MW to 9,800 MW last year, though that still results in a contribution of only around 1% of generation, partly due to scale and partly to Germany's low solar insolation. Wind and solar output would have to quadruple to fill the kWhs supplied by nuclear power, plus their current part of the mix. This challenge is compounded by the problems of intermittency and low output vs. nameplate capacity of both of these sources. In 2007 the calculated capacity factor for Germany's wind turbines was just 21%, while PV was under 10%. So not only would these sources have to expand by a multiple of the capacity lost from idled nuclear reactors, but much of the incremental output would have to be stored, in order to time-shift it to match demand--combined with time-shifting demand to match the variable and cyclical output from these sources. Power from other renewable sources such as biomass, waste and hydro is much more compatible with normal demand patterns, but more difficult to expand quickly and overcome resource limitations.

Most Germans are intensely practical. That German practicality is in my genes and upbringing, part of which was spent in Germany. I speak the language and know the people fairly well, yet it remains a mystery to me that Germans would choose to pit these two complementary categories of electricity generation against each other, rather than aligning them cooperatively to replace high-carbon coal and natural gas that is largely imported from Russia--hardly the world's most reliable supplier. The answer appears to reside in coalition politics (in both major groupings) and green ideology, the price of which seems likely to rise sharply. German households already pay more than twice as much for electricity as US households, while German industry pays about 250% what its US counterparts pay, and I can only guess at the comparison to Chinese energy costs. Taking large, fully-depreciated baseload power sources out of the national mix will only amplify those disparities. I'd be very surprised if Germany didn't choose a course that hews back towards practicality in the long run.