Europe’s Solar Boom Is Pushing Power Grids to The Limit

By Will MathisTom FevrierHayley Warren October 28, 2025

When an early warning system designed to alert operators across Europe about disturbances on the grid was rolled out a decade ago, the predominant color showing on the on-screen maps was green. Safe with no disruptions.

More recently it has become common for the maps in grid control rooms to light up amber, red, and on occasion even black for blackout. The widely-used traffic light model is a real-time illustration of how solar’s rapid success — with roughly four panels being installed somewhere in Europe every second — is colliding with the limits of a grid built long before renewables became central to power generation.

The situation is getting more difficult to manage and operators say they lack the tools they need to balance out the effects of solar, according to interviews with more than a half-dozen European grid managers. Getting it wrong or failing to act has severe consequences like the lights going out.

“The speed of the change is extreme,” said Jan Vorrink, who ran the control room of the Dutch grid for over a decade. “The strong increase in solar is pushing the boundaries of the system.”

Solar farms are being built faster than even the industry expected. In 2020, Europe installed 23 gigawatts of solar, according to BloombergNEF data. Each year since then a new record has been set, with some 69.2 gigawatts expected to be added this year, capping a more than quadrupling of capacity in the last decade.

By the end of the decade, solar is set to become the largest green energy source globally, according to the International Energy Agency. The shift has been particularly marked in Europe where countries have supercharged the buildout to try and ditch expensive imports of natural gas and deliver on the COP28 pledge to triple global renewable capacity by 2030, crucial to achieving the Paris Agreement’s 1.5C target.

Vorrink now works on designing a control room fit for the future, but he was on the front line at Tennet Holding BV for many years. In 2009 when he was manager, the control room was a calm and quiet place to work. Alarms rarely rang, if ever. Now those alarms go off frequently when voltage surges and the grid becomes overloaded. The entire network is being stretched about as far as it can go, he said.

“We can still handle it, but it’s not easy,” he said.

The question now for Europe is whether it can revamp its grid fast enough to prevent another dramatic blackout. A chaotic shift would play into the hands of political factions across the world who claim that net zero will cripple businesses and make energy more expensive.

A Disorderly Transition

Solar’s popularity has risen as panel prices have declined dramatically. Large-scale manufacturing has driven costs down by about 99% since the 1970s, according to a MIT study published last month.

Because it’s cheap to install, solar is accessible to consumers who want to put a few panels on a rooftop, as well as utility-scale farms spread out over hundreds of acres. The cumulative effect means that the grid can’t mitigate the impact of high voltage when it occurs on such a large scale. In June, solar was the biggest source of electricity in the European Union for the first time, an increase of 22% from a year earlier, according to data from thinktank Ember.

If only a few homes in a neighborhood have solar panels, it’s manageable, but when nearly all of them do, it becomes much harder to control, Tennet’s Vorrink said.

The fragility of the region’s electricity network came into focus earlier this month when Spain’s grid operator asked for emergency measures to control sharp increases in voltage. Red Electrica said it noticed the surges during times of low demand and high solar production and warned that it could lead to a cascade of disconnections, reminiscent of those that caused the worst blackout in Europe in decades. The outage, earlier this year, affected more than 50 million people in Spain and Portugal and shows what’s at stake.

In the aftermath, many were quick to blame solar. It’s clear from evidence published so far that the sudden disconnection of a large amount of solar did contribute to high voltage on the network, which ultimately brought down the system. And the issue hasn’t gone away.

Voltage is the electrical pressure that pushes electrons from power stations through the grid to consumers. Networks need to be kept steady and if the voltage starts to move outside the boundaries set by the control room, alarms will sound that there’s a problem somewhere.

It’s not just Spain, surges in voltage are happening more often in Europe with the rapid addition of renewable power generation. In 2024 there were a record 8,645 instances when voltage rose above allowed European limits. That’s more than a 2,000% increase from 2015, when there were 34 alerts, according to data published by the European Network of Transmission System Operators for Electricity, known as Entso-e. That’s like getting an alert almost every hour, up from fewer than three times a month a decade ago.

When there’s an increase in voltage, other devices connected to the grid including power stations, may automatically disconnect to protect them from damage. This has the effect of raising the voltage even further. In a worst-case scenario the cycle continues until the whole network goes down like it did in Spain.

For decades, low voltage was the more common problem and grid operators developed tools to manage it. Solar has turned the status quo on its head.

Grid operators have started to respond. Germany enacted a law earlier this year to try and discourage solar farm operations from producing more power than consumers can use. Italy has been buying up new equipment to stabilize the grid in ways that fossil fuel plants have typically done. And following the report on Spain, the pan-European grid operators group Entso-e is calling for changes to regulation that would force renewable generators to help keep voltage under control.

Market Distortions

The flood of solar power is causing disruption beyond just voltage. It’s become common for wholesale prices to fall below zero. Solar and wind have no fuel costs, so there’s little incentive for operators to switch off when prices fall. When there’s low demand and lots of renewable supply, prices can turn negative.

Europe’s biggest power market Germany has the largest fleet of solar and wind in the region. It also has a rapidly rising number of negative prices. In 2019, about 2% of hourly power contracts traded below zero. By last year, the figure had more than doubled to 5.2%.

At first glance, the investment outlook isn’t encouraging. Solar farms selling directly into the market must pay if they generate when prices turn negative. Even projects with guaranteed contracts face shrinking returns as demand continues to decline. Yet, developers remain undeterred — a trend that has caught grid operators off guard, said Stefan Kapferer, chief executive of 50Hertz Transmission GmbH, which runs the grid in northeastern Germany.

“We have a similar trend across Europe: there is a lot of investment in solar capacity and demand is flat,” 50Hertz’s Kapferer said. “That makes no sense.”

In the spring of last year, power grid operators in Poland made an urgent call to colleagues in Germany, according to Kapferer. Large amounts of solar were expected to overload the Polish electricity system and the authorities needed the Germans to take as much of the excess power as possible to keep the lights on.

The same thing happened on some weekends in 2024, Kapferer said. Each time the excess power was offloaded successfully without anyone’s lights flickering but Kapferer worries that more extreme measures like controlled blackouts will soon be needed.

“It could happen that we have to temporarily switch off the power supply in some districts,,” he said. “That is not happening now, and we are working to ensure that it does not happen, but if the development continues as it has in recent years, it is a growing risk.”

Equipment like transformers, which change voltage and make electricity safe to use, are crucial to the grid and hard to replace. If they get overloaded with too much power, they can break and the lead time for getting a new one is as long as five years. It can be better to shut off an area of the grid to protect equipment.

“It’s much easier to disconnect a consumer for one, two, three, or four hours to protect the equipment than to let the equipment be damaged and leave the consumer without electricity for months,” said Konrad Purchala, vice-president responsible for system development at Polish grid operator PSE.

Bits of Kit

There is specialized equipment that can help. A synchronous compensator has huge metal cylinders containing rotors that spin 1,500 times per minute to help keep the grid stable.

Solar panels and batteries rely on a device called an inverter, which converts electricity from direct current to alternating current for household use. Inverters can also adjust and optimize voltage levels. One possible fix for today’s grid instability is to tweak existing inverter settings so that solar installations respond to voltage spikes instead of automatically shutting down, as many do now.

While retrofitting older systems may be difficult, new solar and battery projects can be equipped with smarter inverter settings to help stabilize grid voltage. It’s evident new rules will need to be drawn up to manage this growing problem.

“We need generation that has voltage control” either conventional or renewable, Damian Cortinas, chair of the board at Entso-e, said earlier this month in a presentation of the report on Spain’s blackout. “We are going to advocate clearly for changes in regulation.”

Grids are regulated in five year investment cycles. This means they’re generally moving at a much slower pace than the private capital developing solar and wind farms. Getting new rules agreed also takes time.

“These are long-term measures and will not have an immediate impact,” said Olivier Arrivé, co-chair of the systems operation committee at Entso-e who is part of the team of experts investigating the Spanish blackout.

Some countries in Europe already have synchronous compensators, but as the penetration of renewables increases, they will need more. Spain had none in operation on the mainland on the day of the blackout. If they had, the blackout could have been avoided.

The cost of creating this extra stability will ultimately be passed on to consumers. A synchronous condenser in Liverpool, England built by Norway’s Statkraft AS cost £25 million and has a contract with the grid manager. It’s an example of how these assets could be operated and paid for in countries around Europe too.

Getting Worse

Solar power has surged all over the world with a particularly sharp ramp up in Europe. In Spain, for example, solar power made up about 21% of total electricity generation last year, up from less than 6% five years earlier. China got some 8% of power from solar farms last year, while the US got less than 7%.

China and the US have added the most capacity but those nations have also experienced a jump in demand for electricity from data centers and economic growth. In the EU, the sharp increase in natural gas prices beginning in 2021 has contributed to a contraction in demand of more than 5% below pre-pandemic levels, according to data from the Brussels-based climate and energy think tank Ember.

More renewables are coming. The European Commission has proposed a goal to cut its emissions by 90% by 2040. The EU will need to rely heavily on a rapid expansion of wind and solar if it’s going to even come close to achieving that target.

As more renewables are added to the system, increased investment is needed into ways to manage grids safely, according to Mehdi Ghazavi Dozein, a lecturer in power and energy Systems at Monash University in Melbourne Australia.

“People are talking about 100% renewables and we are going to get to that point, but we need to be very aware of this risk and plan ahead,” said Ghazavi Dozein. “Spain is not going to be the last blackout to happen.”