Taking stock of a few extremely sunny months in a row
After months of continuous sunshine, the weather has finally changed. The rain that many farmers were longing for has finally arrived. A good moment to take stock of this exceptionally sunny period.How easy it is to get used to wonderful weather! After months of continuous periods with nothing but sunshine from early morning until late in the evening, it feels strange to experience ‘normal’ Dutch weather again, such as your typical ‘changeable with the occasional shower’.
Your solar panels will certainly be happy that they are finally being rinsed clean again, but even without this cleaning they undoubtedly generated record amounts of energy for you in recent months. Let’s see what it was like.
Record amount of sun
The amount of sunshine was phenomenal. The picture below shows the number of hours of sunshine per day in the period from 1 March to 26 May this year, measured in De Bilt (source: KNMI). The blue bars indicate the maximum possible duration per day; this increases over time because the days are getting longer. Yellow is the measured number of hours of sunshine per day. The picture makes clear that the sun shone almost every day from morning to evening.
The amount of yellow in this picture shows how much sun there has been recently (source: KNMI)
If we compare this image with the same period last year, the difference is immediately clear: In the 2024 image below, there's a lot less yellow:
Far less yellow to be seen in the same period in 2024 (source: KNMI)
The abundant sunshine provided record amounts of clean solar power in the grid. There were several times when there was so much solar energy that the whole of the Netherlands could be supplied with sufficient power from just the production of solar panels.
Three days with negative power prices
Such an enormous supply resulted in low prices on the EPEX spot market, and therefore low prices for those with a dynamic energy contract. There were even a number of days with negative prices, namely: April 27, May 1 and May 11. On May 11, the price even briefly dropped to -27 cents per kWh (see graph)! On a day like that it's worth temporarily switching off the solar panels, even if such days only occur very sporadically.
Negative all-in electricity price on May 11, 2025 (source: Energy Zero)
It would be better if the inverter would automatically switch off when there are negative electricity prices, instead of you having to do it manually. And if the system would also charge electric cars, operate heat pumps and charge batteries based on varying electricity prices, it would be absolutely great! Inverter manufacturer SMA is working hard on it: in Germany they've already started (with the launch of a collaboration between SMA and energy supplier Lichtblick), and in the Netherlands it should be happening in the third quarter of this year, for people with a system including a Sunny Home Manager. In contrast to the German situation, Dutch consumers with SMA systems will not be tied to one specific energy supplier. As soon as more information is announced, we will let you know immediately.
Imbalance market lags behind
The earnings on the imbalance market have been a bit disappointing in the past month. Perhaps it was because the supply of energy on all those cloudless days was very predictable: after all, the imbalance market depends on incorrect predictions, which results in power having to be ramped up or down at the last moment. Energy supplier Frank Energie shows the so-called ‘trading index’ in their app for each day. You can find this by clicking on ‘Smart home’ in the app, then on your ‘home battery’ and finally on ‘trading results’.
In the Frank Energie app you can find the 'trading index' per month or per day, for example for May 25, 2025 it was 26. The higher the index, the more money there is to be made on the imbalance market; the average index value is 100
Plotting each day's trading index value on a graph for the past three months, we get this:
The trade index over the past months remained clearly below average, with only a handful of outliers (source: Frank Energie)
Frank Energie bases the expected yield in a year on an average trading index of 100. It's clear that the trading index has been well below average on most days in recent months, with a few outliers. As a result, the income that people with a home battery could earn on the imbalance market has been rather disappointing.
Hot summer 2025?
It is quite possible that the imbalance market will pick up again in the near future, because the weather outlook predicts more changeable weather. Furthermore, the days will of course become a little longer, which means that solar panels could produce just a little more energy, although the longest day of the year is quickly approaching. We don't expect many more days with negative electricity prices: last year, after May, there was only one more day that had prices dropping below zero.
What is quite possible is that it will be a hot summer. Researchers from the Max Planck Institute in Germany have shown that a build-up of heat in the Atlantic Ocean leads to above-average hot summers in Europe a few years later. Based on this research, the cautious conclusion is that the summer of 2025 could also be hot again.
The prospect of a hot summer is a good reason to invest in some cooling, don't you think? Solar panels on the roof help to lower the temperature in the attic, and our Daikin air conditioning systems ensure, in addition to heat in the winter, a fresh indoor climate in the summer. So don't wait until it's too hot to pick up the phone; call us now, we're ready to help you!