The number of electric vehicles, heat pumps, solar panels and home battery storage systems is growing rapidly amid the green transition. Estonia's energy sector development plan forecasts that by 2035, 80 percent of new passenger cars sold in Estonia will be electric vehicles and the number of heat pumps will have at least doubled. But the green transition is not only about new cars and heating solutions — it is changing the entire operating logic of the electricity system. The question is no longer whether these changes are coming, but whether our power grid is ready for them.

Recent studies conducted at Tallinn University of Technology show that the simultaneous use of these new devices could increase the load on Estonia's distribution networks by as much as fivefold. This is not a theoretical risk, but a realistic scenario in a situation where electricity covers the vast majority of our daily energy needs.

Looming changes

Until now, the electricity grid has been built on the logic that electricity flows from large power plants to consumers and that demand grows slowly and predictably. The green transition has turned that logic upside down.

Consumers are now simultaneously producers and flexible users of electricity. Electric vehicles are no longer merely a means of transportation, but major mobile electricity consumers. Heat pumps are replacing fossil fuel-based heating systems. Solar panels feed electricity back into the grid. All of this means electricity is generated and consumed in a far more volatile manner, while large amounts of power now flow through the grid in both directions.

When thousands of electric vehicles begin charging simultaneously at the end of the workday and heat pumps switch to full capacity on a cold winter evening, peak loads emerge that the grid was not originally designed to handle. Such overlapping demand causes overloads and voltage problems, creating the need to reinforce the grid.

This is particularly acute in sparsely populated areas where power lines are long and consumers are spread out. Because of the long transmission distances, voltage drops are greater and reserve capacity is smaller — meaning the critical threshold is reached faster there than in more densely populated urban areas.

In Ida-Viru County in particular, the situation is even more sensitive, as both the region's economic structure and its energy system are being reshaped at the same time. The transition away from fossil fuels and the move toward electrification must take place in a way that does not place additional strain on the region.

New devices and their true effect

I analyzed this issue in my master's thesis, focusing on a suburban residential development where electric vehicles and heat pumps are already part of everyday life. The analysis covered various scenarios, ranging from the conventional addition of such devices to smart control systems in which electricity use is scheduled.

The results clearly showed that when electric vehicle charging and heat pump operation coincide in time, the load in some parts of the grid can increase fourfold to fivefold. Electric vehicles create short-term but very high peaks. Heat pumps, meanwhile, keep demand elevated over a longer period. Together, they significantly alter the grid's operating regime.

The analysis also found that if high-capacity devices are installed freely in more than roughly 40 percent of buildings, overloads begin to occur in older network areas. In sparsely populated regions, that threshold may be reached even sooner. Charger capacity plays a major role here: 3.7-kilowatt chargers are considerably less burdensome for the grid than the 11-kilowatt systems that have already become standard.

Solar panels and batteries add another layer to the equation. While solar panels reduce the grid's overall load, they also create periods when electricity flows back into the network. When there are many such producers, managing the grid becomes more complex. Battery storage systems help balance the situation by smoothing out peaks and increasing local consumption.

Previous planning models assumed stable and predictable electricity consumption. In reality, however, consumption patterns have become far less predictable and much more dynamic.

Effects on consumers and solutions

All of this combined could mean connection restrictions, larger grid investments and, in the long run, higher network fees. At the same time, it also means the consumer's role is becoming more active: people can already schedule electric vehicle charging or intelligently manage the operation of their heat pumps on a daily basis.

In other words, the question in the future will not only be how much electricity we consume, but when we consume it.

From the grid's perspective, the solution does not lie solely in building thicker cables. What is needed is a change in grid planning methodology so that it takes into account overlapping demand, distributed generation and regional differences. A balance must be found between grid investments and smart management solutions.

I am currently working on my doctoral dissertation under the supervision of Argo Rosin and Vahur Maask, focusing specifically on these issues. My research examines how to realistically assess the spread of electricity demand and critical thresholds and how to design the grid so that the green transition is both technically viable and economically reasonable — in cities as well as in Ida-Viru County.

The electricity grid is like a rural road: if too many heavy trucks are directed onto it at once, the road must either be widened or traffic managed more intelligently. Estonia must now decide how to do this before the road becomes too narrow.

The conclusions are based on studies conducted as part of the Just Transition Fund project "Research and Development of Innovative Renewable Energy Production and Flexibility Technologies."

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