What should be considered when buying an electricity storage

MORE THAN 50% OF NEWLY INSTALLED PV SYSTEMS WITH STORAGE

Today, more than half of newly installed solar systems are already equipped with battery storage. There are good reasons for this: Households can significantly increase their own consumption with the help of solar power storage systems by storing energy generated during the day and making it available again, especially at evening times when electricity demand is higher. Even with a small storage system, the self-consumption of many households can be increased to over 50%. Especially against the background of rising electricity prices, storage systems are now becoming increasingly popular.

VARIETY OF BRANDS AND MODELS IS BECOMING INCREASINGLY CONFUSING

But consumers are now confronted with an increasingly confusing range of products. Due to rising demand, not only the number of suppliers but also the number of individual models has grown considerably in recent years. This is not least due to the automotive industry, thanks to its increasing investments in the field of electromobility. Given the variety on the market, it is often difficult to keep track of the different models available - especially after a number of suppliers have just launched or announced new models.

But what should you look for when choosing the right storage device? Here we list the ten most important criteria according to which storage devices can be differentiated. The weighting of the individual points depends, of course, on the individual needs and conditions.

AC CONNECTION

There are single-phase and three-phase inverters. The latter are gaining acceptance because they enable a uniform feed into the power grid, whereas with single-phase inverters there is a risk of asymmetries in the grid voltage. If larger consumers (such as an electric stove, sauna, e-car charging station or machines) are to be supplied, a 3-phase system is necessary.

BACKUP POWER FUNCTION

If a storage system has a backup power function, it can supply the building with backup power within a few seconds in the event of a power failure, thus bridging the outage.

WARRANTY PERIOD, REMAINING CAPACITY

Generally, storage manufacturers specify three values in the warranty - the cycle life, the calendar life and the available remaining capacity. The cycle number indicates how often the memory can be fully charged and discharged. Partial cycles, e.g. the memory is only discharged to 50% twice, also correspond to a full cycle. The residual capacity shows how much of the storage tank is still usable after the specified number of cycles or after the specified number of years (whichever comes first). For a single-family home, one usually achieves between 200 and 250 full cycles per year, so after ten years, one would get up to 2,500 charge cycles.

RATED POWER (CONTINUOUS OPERATION)

The nominal power, also called bottleneck power, indicates the power in kilowatts (kW) with which the storage unit can be charged and discharged. For example, a hair dryer requires about 1.8 kW.

USABLE CAPACITY

The gross capacity indicates how many kWh are available in a storage unit. Due to their design, lithium storage units cannot be completely discharged in order to avoid damage to the cell technology. For better comparability, we have therefore compared the usable capacities in this comparison.

PV SYSTEM DIRECTLY CONNECTABLE

To generate electricity from PV systems, you need an inverter with PV input, also called MPP (Maximum Power Point) input. The PV modules should be connected to their own MPP input depending on their orientation (south, east or west).

SYSTEMS CAN BE CONNECTED IN PARALLEL

To achieve more power or capacity, many storages offer the possibility to connect systems in parallel.

TECHNOLOGY

Almost all products on the market rely on either lithium-ion or lead-acid batteries. However, there is now a clear trend toward lithium-ion batteries because they offer several advantages over lead-acid technology, including a significantly higher number of charge cycles and a greater depth of discharge. Within the Li-ion batteries, a further distinction is made according to the respective cell technology. Cells based on lithium nickel manganese cobalt oxides (NMC) and lithium iron phosphate (LFP) are particularly common. In addition to the high level of safety and longevity, we believe that the high recycling rate is a particular advantage of LFP. According to today's standards, more than 90% of LFP can be recycled.

UPS FUNCTION

This function ensures an uninterruptible power supply. In the event of a power failure, the memory then switches over at lightning speed, allowing sensitive loads such as televisions, servers, etc. to continue to operate.

AVAILABILITY

When will the corresponding storage units be available on the market or what is the distribution concept behind it, i.e. by what means and at what locations can they be obtained?

With this information you are well prepared for further research - we hope that we were able to support you a little bit in further narrowing down the right storage. If you have any further questions, our experts will of course be happy to advise you.

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