Nuclear power was eleven times more efficient than solar power in 2023

The original article can be read as “Schlumpfs Grafik 114” in the online Nebelspalter of 3 June 2024.

Next Sunday, we will vote on the federal decree for a secure electricity supply with renewable energies. If this Electricity Act is adopted, the expansion of photovoltaics in particular will be promoted. However, despite a record increase in the number of solar installations last year, the yield balance of these installations is extremely poor – especially when compared with that of nuclear power plants.

What is important:

– In 2023, the installed capacity of solar power plants in Switzerland was just over twice as high as that of nuclear power plants – but the electricity yield was five times lower.
– This means that the capacity utilization of solar power plants was eleven times worse than that of nuclear power plants over the entire year.
– In one month alone (December 2023), however, solar utilization was almost 60 times worse than nuclear – and on the sunniest day of the winter it was over 2,000 times worse.

This fact check compares the capacity utilization of solar and nuclear energy over different time periods. All figures used here come from the website “Swiss Energy-Charts” (see here). This website is run by TNC, a solar company that is listed by the industry association “Swissolar” as a so-called solar professional (see here).

Capacity utilisation indicates how efficiently an electricity generator can convert its installed output into work (equal to electricity). This involves calculating the percentage of time it produces at full load. The following graphic shows the necessary parameters for the year 2023:

The gray bars show the installed capacity in megawatts (MW), the red bars the electricity yield in gigawatt hours (GWh) – on the left for the nuclear power plants, on the right for the solar power plants.

Only 8.2 percent utilization of solar systems

The decisive factor for all further calculations is that at the end of 2023, solar power plants had an installed capacity of 6240 MW, which is more than double that of nuclear power plants at 2960 MW. However, at 4480 GWh, the electricity yield was around five times lower than that of the nuclear power plants at 23,510 GWh.

So how high was the capacity utilization of the solar installations? 54,660 GWh of electricity can be produced from 6240 MW in 8760 annual hours. The 4480 GWh actually generated are 8.2 percent of this. The same calculation for nuclear power plants results in a utilization rate of 90.7 percent. This means that in 2023, solar power plants had a utilization rate eleven times lower than that of nuclear power plants.

However, this poor balance for photovoltaics is still glossed over. Because in a winter month, this comparison looks even worse. The next chart from “Swiss Energy Charts” shows consumption and electricity generation in Switzerland in hourly resolution in December 2023:

The consumption (load) is shown as a black line at the top. The different types of electricity generation are cumulated from below: Nuclear (red), run-of-river (dark blue), storage water (light blue), pumped storage (turquoise blue), wind (light green) and solar (yellow). The difference between consumption and net electricity generation was offset by imports and exports of electricity.

In December 2023, solar had only 1.7 per cent capacity utilisation

The chart above shows at a glance how efficiently the various electricity producers utilised their potential output: NPPs almost always utilise 100 per cent of their potential of 2960 MW (red band power base). In contrast, there is practically no sign of solar power at the beginning of the month. After that, you can recognise the typical midday peaks, which are very small at this time of the year, followed by long gaps at night.

Nuclear power produced 2190 GWh of electricity in December, solar power plants 79 GWh. This corresponds to a capacity utilisation rate of 99.5 percent and 1.7 percent respectively: nuclear power plants were therefore 59 times more efficient than solar power plants.

The next graph shows what this means in concrete terms for solar power plants:

In the same diagram as before, only the electricity consumption and production of solar power are now shown. I have also shown the installed capacity of the photovoltaic systems (6,240 megawatts) with a yellow line: if this same capacity were installed in the form of nuclear power, Switzerland would become an electricity exporter in winter. However, if it is installed in the form of PV modules on house roofs, the yield is meagre – the systems usually fail completely.

On December 4, only 0.04 percent of the photovoltaic capacity was utilized

As mentioned above, there were several days with virtually no sun at the beginning of December. For example, the capacity utilization of PV systems fell to 0.04% on 4 December. Compared to the 100 percent capacity utilization of the NPPs on that day, this is a factor of 2,500 less efficient.

In view of the blatant winter weakness of solar power, it remains a mystery how a secure power supply can be guaranteed with a significant increase in PV systems. But this is what the Electricity Act promises us.