Californian solar is much more reliable than German solar

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I explained yesterday that Germany is never going to run on solar power for the simple reason that it is too far north and too cloudy. Winter is simply too much of a problem for high latitude countries to get very far with solar power.

Things, of course, are a lot different in sunnier southern locations. So let’s compare Germany with California.

As I’ve written before, CAISO produces hourly output data for all renewables in California. This let’s us make simple and instructive comparisons with Germany.

First I will look at mean daily output. Here is main daily output for each day of last year in California and Germany. I have set the axes so that maximum output is aligned for both regions.


Californian solar is clearly much more reliable than German solar, both seasonally and in terms of day to day variations. The effect of winter (where German solar panels produce almost nothing for long stretches) is much less of an issue in California.

However, individual days can still be a problem in Calfornia in winter. Mean output of Californian solar last year was 1191 MW. But the worst day was 2nd of December when output averaged 162 MW. This was 14% of the average. That low raises obvious questions about the ability of Californians to abandon the grid and run on solar and batteries. You would need to have to store more than you would prefer.

The differences between California and Germany are even clearer if we look at monthly averages.


Consider January. Relatively speaking, California solar produced around three times more that month than German solar did. This is a massive difference.

Monthly output of German solar varies by more than a factor of ten. In fact, June output was almost 13 times greater than the output in December.

California is much more stable, with monthly output varying by approximately a factor of two.

To say that the prospects for solar are greater in California than they are in Germany would be an understatement.

Note on data

California solar data was downloaded from CAISO and German data was downloaded from the website of PF Bach. Data was analyzed in R, and I have plotted it using ggplot2 and a custom theme. Code can be provided on request.

5 thoughts on “Californian solar is much more reliable than German solar

    MorinMoss said:
    August 13, 2015 at 1:49 am

    I imagine the same would be true of almost the entire Southern USA so it’s perplexing why Texas installed so many wind turbines and so little solar.
    TX generates 3x as many MW-hrs from wind turbines as does CA but only 4% as much from solar.


    donoughshanahan said:
    August 13, 2015 at 10:52 am

    You were looking for energy data sources; anther for CA solar. Good luck with the papers.


      Robert Wilson said:
      August 13, 2015 at 4:26 pm


      I hadn’t seen this before. Maybe a blog post here.


    Jarmo said:
    August 15, 2015 at 7:59 am

    The comparison would be clearer if both tables used % of max. output. The massive difference would really stand out.


      Robert Wilson said:
      August 15, 2015 at 9:04 am


      The plots are already aligned so that maximum output is at the same height. So I thought it was relatively clear to begin with.


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