I write repeatedly about my number two pet peeve: the continued use of renewables capacity figures to show the rate at which renewable energy is growing. This is problematic for a number of reasons. First, it lumps wind, solar, and hydroelectricity into one category despite the fact that they all have very different capacity factors.

As a result it makes it seem that solar is growing more quickly than it really is in relation to wind and hydro. But more importantly, looking only at capacity makes it seem as if renewables are growing much more quickly than they really are in relation to fossil fuels.

A good example of the use (and abuse) of capacity figures come from Friends of the Earth. Here is how they describe solar in Germany:

In Germany, the amount of solar power installed grew from 2 Megawatts (MW) in 1990 to 37 Gigawatts (GW) in 2014 – 37,000 Megawatts. That’s equivalent to nearly half of the UK’s entire power generating capacity. On one sunny Sunday in May 2014, Germany’s solar panels and other renewables provided almost 75% of total national electricity demand. [My italics]

It is hard to imagine a more misleading string of statistics. The above numbers will lead the average reader to imagine that solar power in Germany makes up the majority of supply and is the equivalent of half of Britain’s grid. Yet, last year Germany got 34.9 TWh of electricity from solar panels, whereas Britain generated a total of 335 TWh of electricity from all of its power plants. Instead of being the equivalent of half of Britain’s electricity grid, German solar is the equivalent of 10% of it.

This is what happens when you install solar panels in high latitude and cloudy countries: innumerate environmentalists get confused.

A more common issue is the continued plotting of the growth of renewables and other forms of electricity on a single graph using capacity only. The following graph of future additions to global electricity generation appeared in a recent Bloomberg article:

This fairytale figure is misleading in numerous ways. Solar capacity additions appear to be much greater than fossil fuel additions over the next 25 years, yet in generation terms they will clearly be lower.

The graph, if it is to be meaningful to the average person should not be in terms of capacity, but generation.

Let me show this further by comparing solar and nuclear in Germany in the two graphs below. On the left we have the commonly used capacity graph. On the right is a graph showing actual generation from nuclear and solar. The one on the left tells a very different story the to the one on the right. The reason is simple. German’s nuclear power plants produce around 9 times more electricity per unit capacity than their solar panels do.

The above graph should make it clear. Capacity only graphs are misleading. Now, if only we could pass a law to ban them.