Lithium storage for the solar system - a sensible purchase?

More and more homeowners today decide to install a solar system. Rising electricity prices are just as much a reason for this as a growing sense of responsibility towards the environment and the resources of our world. In addition, solar power systems have become increasingly cheaper in recent years, which has lowered the inhibition threshold for this investment.

Why energy storage?

To operate a solar system, not only photovoltaic modules are required, but also solar power storage. Theoretically, such a system could also be operated without an energy storage device, but this would mean having to accept significant disadvantages. In times of greatest solar activity, potential for generating electricity would be wasted, while at night one would still have to rely on energy from the grid. A solar power system is therefore only fully profitable with an associated solar storage tank. Lithium batteries have gained increasing popularity as a storage solution for solar systems in recent years and are now emerging as an equivalent alternative to the well-known lead storage.

This is how lithium storage works

The electrochemical reaction that takes place in lithium batteries is relatively easy to explain. During the charging process, the lithium ions migrate from one electrode to the other through an electrolyte and remain there. When discharging, the lithium ions move in the opposite direction, releasing the stored energy again. The electrodes are usually made of graphite, but models with iron or cobalt conductors are also available on the market.

The advantages of lithium batteries

Image source: Tesla

The advantages of lithium storage compared to other solutions are immense. On the one hand, they have a longer service life than lead-acid batteries. Current models can be used to store electricity for up to 20 years. The number of possible charging cycles is also much larger than with lead-acid batteries. In addition, the lithium storage can be discharged more deeply without suffering permanent damage. Modern lithium storage devices have practically no memory effect and have a low tendency to self-discharge. With the same storage capacity, lithium batteries are also smaller and lighter than lead batteries. As a result, they take up less space in the household and systems with a larger capacity can be installed with the same space requirement. The efficiency is also significantly higher than with lead-acid batteries. These can only store about 80 percent of the incoming electricity, the rest they give off as waste heat to the environment. Lithium batteries today have efficiencies of 90 to 95 percent. Since they do not outgas, unlike lead batteries, they do not have to be installed exclusively in well-ventilated rooms.

The course of the day with a solar power storage

Disadvantages of lithium-based batteries

However, these energy stores also have some disadvantages. The main reason for deciding against lithium-based photovoltaic storage systems is probably still the high price. At the moment, the cost difference between photovoltaic storage systems made of lead or lithium is around a factor of 2.5. However, this difference is compensated for by the almost twice as long service life of the lithium batteries, which, however, only pays off after many years of use.

Of course, government subsidies, such as the KfW Bank, can reduce the cost of the purchase, but these advantages also apply to the cheaper lead-acid batteries. The costs are caused both by the raw materials and by the complex charging electronics, without which this energy storage device would not be functional. Incidentally, lithium reacts strongly with air and water, which can lead to explosive reactions. The electrolyte it contains is also flammable. However, there is practically no danger from undamaged solar power storage systems if they are handled properly.

Last but not least, the environmental balance of lithium batteries is not unproblematic. Lithium, as well as the metal cobalt, which is also required for production, are rare raw materials. They are also harmful to health, so recycling lithium batteries is complicated. This is offset by the fact that this type of battery can provide years of service without having to be replaced, meaning that lithium batteries need to be recycled far less frequently than their lead-based counterparts.


Ultimately, there are many arguments in favor of lithium-ion storage as an alternative to lead-based batteries, especially since lithium storage is constantly becoming more powerful and better. However, their own rapid progress also harbors reason for hesitation: the development is far from over here. Lithium-ion storage prices have fallen 30 percent over the past three years. Forecasts assume that by the year 2020 price reductions of another 50 percent can be expected. The storage densities and efficiencies of the batteries will also continue to increase, even if a high level has already been reached here. It is in the eye of the beholder whether it makes sense to purchase a lithium storage unit for your own system or whether you should initially opt for the cheaper lead storage unit in order to switch to a better and until then cheaper lithium model in a few years. Suitable new or used variants as well as remaining stock, stock and B-stock can always be found on the SecondSol online marketplace.