Energy Transition – The self-deception is real.

Battery storage systems are an important component of the energy transition – but what happens to the costs?

What battery storage can do – and what it cannot: a calculation for Leipzig

When people talk about the energy transition, battery storage almost always appears as part of the solution. And rightly so. Without storage, a power system with a high proportion of wind and solar energy is more difficult to operate. Batteries can balance frequency fluctuations, smooth out power peaks, shift solar power to evening hours, and relieve the load on power grids.

The problem only begins where a useful tool is turned into an alleged total solution.

Because a storage system is not simply "big" or "small." The crucial factor is the task it is supposed to perform. Is it intended to bridge seconds? Hours? A whole day? Several days? Or even seasonal differences?

It is precisely this distinction that is lost in many debates.

The simple difference between power and energy

Power describes how much electricity is provided or consumed at a given moment. Energy describes how long this power can be provided.

One kilowatt over one hour results in one kilowatt-hour.

This is the central rule of calculation. It sounds unspectacular, but it is the point where many political and media simplifications fall apart.

Leipzig as a scale

For Leipzig, the scale can be shown quite roughly. Official statistics for electricity and local district power show an annual consumption of around 2.256 TWh. This corresponds to an average annual continuous load of approximately 258 MW.

This results in the following storage sizes:

This table already shows the core problem: The step from a few hours to several days is not a small addition. It is a leap into a different order of magnitude.

What that means financially

For large battery storage systems, you can roughly calculate 160 to 300 euros per kWh. This is a rough range, not a specific project calculation. However, it is enough to make the dimension visible.

For Leipzig, this would result in:

And we are not even talking about land, grid connection, substations, fire protection, operation, maintenance, aging, redundancy, or permit risks. This is only about the theoretical storage capacity.

In short: Battery storage is plausible for short-term shifts. For longer supply gaps, they become extremely capital-intensive very quickly.

The material question

Money is only part of the calculation. Batteries consist of real raw materials that must be mined, processed, transported, and installed.

For LFP systems, one can roughly calculate with the following material intensities per kWh:

A storage system intended to theoretically supply Leipzig for seven days would therefore amount to roughly:

These numbers are not intended to dramatize. They are only meant to make the physical side of the debate visible. Energy systems do not consist of PowerPoint slides, but of plants, cables, power electronics, raw materials, land areas, and supply chains.

Calculated illustratively: Home storage and large-scale storage

A typical home storage unit is designed for a house, not a city. Nevertheless, the comparison is helpful because it makes the scale tangible.

A Tesla Powerwall has 13.5 kWh of usable capacity.

For Leipzig, this would mathematically correspond to approximately:

With industrial large-scale storage, the number of units naturally looks better. If you calculate with a Megapack of about 3.9 MWh, the result is:

Again, the following applies: This is no argument against this technology. It is an argument for honest standards.

Electric cars as a storage reserve

Electric cars can play an important role in the future. If many vehicles can charge bidirectionally, a large, distributed flexibility emerges. This can reduce load peaks, relieve local grids, and cushion short-term fluctuations.

But this idea also has limits.

If one takes a typical vehicle battery with 65 kWh and assumes that in everyday life 20 percent of it would realistically be available for the grid, about 13 kWh per car remains.

To theoretically supply Leipzig for just one hour, about 19,800 simultaneously available vehicles would be needed.

And "available" here does not just mean: they exist somewhere in the city area. They would have to be connected, technically suitable, allowed to participate, sufficiently charged, and coordinated.

This is feasible as a flexibility component. However, it is no guarantee for security of supply over longer periods.

The actual planning question

The crucial question is therefore not: "Are batteries good or bad?"

The better question is: "For what time period and for what task are we using them?"

Batteries are strong for seconds to hours. They are excellently suited for short-term grid stabilization. For daily shifts, they can make a relevant contribution. For several days or weeks, you need additional robust solutions. Pure battery logic is not sufficient for seasonal gaps.

A resilient energy system is not created by overstretching one tool. It is created by the clean combination of different building blocks.

Conclusion

Battery storage systems are necessary but not infinitely scalable. Using the example of Leipzig, it becomes visible how much the need for storage, costs, material quantities, and infrastructure grows as soon as one no longer talks about hours, but about days.

This is not a rejection of batteries. On the contrary: those who want to use batteries sensibly must know their strengths and respect their limits.

They are a very good tool for short-term flexibility.

However, they are no substitute for a complete system architecture.

Sources and calculation basis

• City of Leipzig / Open Data: Annual energy consumption figures, electricity/local power 2,256 GWh/a
• Tesla Powerwall: 13.5 kWh usable capacity
• Tesla Megapack: assumed here roughly at 3.9 MWh per unit
• Cost assumption for utility battery storage: roughly 160 to 300 euros/kWh
• Material assumptions for LFP storage per kWh: Lithium 0.12 to 0.18 kg, Graphite 1.4 to 1.8 kg, Copper 0.5 to 0.8 kg