Why Investing in Wind and Solar to Avoid Gas Shocks Hasn't Added Up for Some

I think, though the article doesn't say this and only vaguely circles the point, it is likely that Spain gets concentrated bursts of solar energy that collapse the marginal price dramatically, while Germany has a more spread out renewable production and so is nearly always burning a little bit of gas.

The very similar amounts of gas burned as a percentage of the total therefore affect marginal price differently.