Just 4 percent extra electricity required to accommodate 1 million electric cars?

My previous post was not completely finished when I learned that our new Flemish Minister of Energy was piggybacking on the resolved delivery problems of the Tesla 3. She wrote a post about the increase in electric car subsidy requests during the first three months of the year and framed it as a success story. It is best making hay when the sun is out.

While trying to find information on the subject of her post, I encountered a tweet in which she answered the question whether we would have enough electricity to supply for electric cars when we already now experience a substantial electricity shortage. I don’t understand the question very well (although our electricity supply is old and in disarray, we don’t have electricity shortages, yet), but her answer is intriguing (translated from Dutch):

Hello Leo, a study by the federal energy regulator shows that for 1 million electric cars, and we are not there yet, you only need 4 percent extra electricity. Doom messages are not necessary.

Tweet Lydia Peeters 20190416

Just 4% extra to accommodate 1 million electric cars? That seems rather low to me. My guess was that this claim originated from some kind of averaging.

Luckily, now I had a source of such a claim: our federal energy regulator (CREG). I was a bit surprised by that, the CREG is our energy watchdog.

One way to find out. I visited their website and went through their publications of the last year, but found nothing matching electric cars. Using their search function didn’t help either.

Broadening my search to the internet helped. I quickly found an article of our public Flemish radio and television (VRT) explaining that we have enough electricity to accommodate 1 million electric cars. It was about a CREG report and, yes, the claim was that 1 million cars would only require 4 percent extra electricity than our current capacity.

These are the assumptions:

  1. Number of electric cars: 1 million
  2. Average mileage of a car: 15,000 km per year
  3. Energy consumption: 0.2 kWh per kilometer

Apparently this seems to be the reasoning:

  1. Total number of kilometers driven per year: 15,000 x 1,000,000 = 15,000,000,000 km
  2. Total energy consumption per year by this movement: 15,000,000,000 x 0.2 = 3,000,000,000 kWh
  3. 3,000,000,000 kWh = 3,000,000 MWh = 3,000 GWh = 3 TWh
  4. We have a consumption of about 80 TWh/year, therefor 3 TWh of 80 TWh is 3.75 or rounded to 4% extra electricity.

Although I was glad that I found the reasoning, I was also disappointed. First, the journalist who wrote this article is one of the few journalists who I respect when it comes to energy reporting. I have to admit that I learned quite a lot about Belgian energy from this guy. Now he seems to be okay with averaging consumption to calculate whether we can accommodate 1 million cars with our current electricity capacity?

Another disappointment was that there was no link to the original report in the article. Nevertheless, now I had some more information. The article was written in October 2017, so chances are that the report would have been published somewhat before that date.

Back to the CREG website and their publication list, but I again found nothing in that time frame. Again broadening my search to the internet, now including the year, gave me more links to articles and posts written about that CREG report.

Luckily, one of them had a link. It went to the 2016 monitoring report Study on the functioning and price evolution of the Belgian wholesale electricity market, published on September 28, 2017. No wonder why I didn’t find anything. This is not exactly the kind of title that I was looking for when searching for reports on the impact of electric cars.

There was a subsection detailing the impact of electric cars on the grid and I recognized the numbers that the journalist used.


Besides the calculation of the impact of 1 million vehicles, the author(s) of the report did the same for 100,000, 250,000, 500,000, 2 million and 5 million vehicles. They then came to the conclusion that our grid, having its current capacity, could accommodate at least 2 million vehicles (except for some days during winter).

This is how the author(s) of the CREG report represented it:

CREG: additional electricity 2016

The graph shows the additional electricity that would have been produced when the grid would work at full capacity (the author(s) used the maximum production in 2016 for that). The blue line is the additional electricity that would have been produced over the full day if production stayed as high as the level of the maximum production in 2016. The difference is of course biggest in summer because electricity consumption is then low.

The orange/brown line is the additional electricity that could be produced at night (between 11 pm and 7 am) compared to the maximum capacity in 2016. The red line is the average consumption of 1 million electric cars, the blue line that of 2 million and the green line that of 5 million.

Because the red line is way below the orange/brown line, they conclude that our grid can accommodate at least 1 million electric cars on condition that loading takes place between 11 pm and 7 am. The 2 million line also stays below the orange/brown line, except for some days in winter, concluding that with 2 million electric cars there will be some days of not (fully) loading.

Purely mathematically, this is perfectly true. If the production stays below the consumption line, then it is possible to accommodate that number of cars. The big question however is how realistic this scenario in the real world? The red, blue and green lines represent the average consumption of electric cars and according to CREG these are all straight lines. That is not hard to understand. The author(s) start with the average consumption of one electric car (10 kWh/day) and multiply this by 1, 2 or 5 million. This gives a perfectly straight lines from January 1 until December 31.

This will never be the case in reality. At our latitude, car users will have the lights and the heater on in the morning and the evening, drawing more power from the battery than in summer. Additionally, batteries discharge faster in cold conditions, leading to less range and more frequent loading requirements in winter. So that line can never be a straight line and will instead peak in winter.

This could well change their conclusion: the blue 2 million line will breach the orange/brown line more often in winter than when it is a straight line. It is even possible that the red 1 million car line also would breach that same line on some occasions in real life conditions.

This averaging of consumption from electric cars also has another effect. The big issue with electric cars is not whether enough electricity can be produced on average, but how many cars are being loaded at the same time. In an electric grid, production has to equal consumption in real time at any time. There are about 36,000 electric/plug-in hybrid cars in Belgium. If they all load at the same time, then they would require the electricity production of a small power plant. Okay, the risk of that happening with the current share is zero, but when electric car use go up (as is projected/encouraged), then the risk of unwanted simultaneously loading will increase.

That risk will also increase when batteries get better and faster to load (being promoted to encourage people to buy an electric car). The faster the battery loads, the bigger the capacity of the loading point needs to be because these will draw the necessary electricity in a shorter timespan. Loading time will be shorter, but that capacity still needs to be available at that moment.

This reminds me of the another case in which electricity consumption is usually averaged. When the media publish about solar of wind installations, they usually make the claim that the installation produces electricity for x number of families. On average this is true, in the sense that the average production of that installation will equal the average consumption of those families. It however doesn’t mean that those families get their electricity exclusively from that installation (they won’t really like the experience). The claim is misleading because it hides the intermittent nature of solar and wind, therefor making it seems like an easy replacement for dispatchable energy sources. By hiding the challenges, the public (and probably also policy makers) will have a too optimistic view of the capabilities of solar and wind.

We see something similar in the case of the electric cars scenario. The author(s) make the claim that our current electricity capacity can accommodate 1 million electric cars and it will only require 4% more electricity. They come to that conclusion after averaging consumption of these electric cars and comparing it with total possible production. It is misleading because consumption of electric cars is not constant over the year, but more importantly, it hides the real problem with consumption of electric cars. That gives a too optimistic view of the impact of electric cars on the grid.

I wonder how this report could ever determine whether in reality our grid can safely accommodate 1 million, 2 million or 5 million electric cars with its current capacity, requiring only 4% extra electricity. It however gave the opportunity to our Minister of Energy to wave away any objections.


2 thoughts on “Just 4 percent extra electricity required to accommodate 1 million electric cars?

    1. trustyetverify Post author

      This is not necessarily the case in this example. She is a lawyer by trade, but she also did Latin-Mathematics in secondary school. That lets me seriously doubt that she is innumerate.

      The problem with the report is not the mathematics part of it. Taking into account all the assumptions used in the report and you will end up with that 4% figure. Purely mathematically speaking, the result of the report is sound. If she already read the report (which I doubt she did), then she could not be faulted by repeating the conclusion of that subsection.

      The problem with that report is the assumption that electricity consumption of electric cars is constant throughout the entire year, which is not the case in reality. But to find that requires reading the whole subsection and understand what the author(s) is/are doing.

      Averaging consumption allowed the author(s) to state their case more optimistic than warranted in reality (there will be more consumption in winter, which is the period that makes a difference for the result of the report) and also to dodge the real-world impact of 1 million electric cars on the grid.

      It is absolutely no problem to deliver the average electricity needed by 1 million electric cars spread over 1 year. There will be lots to spare, even in a scenario including 2 million electric cars.
      There would however be a real problem when even a small percentage of those 1 or 2 million car owners decide to (fast) load their car around the same time at the wrong moment when the necessary capacity is not available.



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