August 31, 2023, 8:59 am | Read time: 3 minutes
No solar system without a battery storage unit–at least that’s a common belief. This isn’t inherently wrong, but there are some misconceptions on the topic. An expert explains what’s really going on.
In 70 percent of new photovoltaic systems, a power storage unit is also installed. This allows the energy generated to be used even when the sun isn’t shining. The additional investment is worthwhile but comes with higher costs. “It’s important to be aware of your personal goals for using photovoltaics in conjunction with a battery storage unit and then thoroughly inform yourself,” advises Stefan Hoffmann, an energy expert at the Consumer Center NRW. In this context, he also mentions some misconceptions about power storage and reveals what’s accurate.
Advertisement: Solar Power Storage – Prices, Power, Practical Tips
Overview
1. Misconception: Power storage cannot be retrofitted
According to the consumer advocate, this statement is false. If it’s a PV system with a so-called hybrid inverter, a power storage unit can be integrated later. This is also true for a “normal” inverter. It doesn’t matter if the system has been in operation for years.
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2. Misconception: The bigger the storage, the better
Does size matter? Not necessarily in this case. Currently, power storage units with large capacities in kilowatt-hours (kWh) are still quite expensive. To keep the system economical, don’t overdo it when purchasing, recommends Hoffmann. He offers a rule of thumb: 1,000 kilowatt-hours of annual electricity demand justify one kilowatt-hour of storage capacity. The annual electricity demand refers to the expected consumption of household electricity, excluding heating electricity and electricity for e-mobility.
But the size of the solar system can also be a limiting factor for the appropriate battery storage capacity. A small PV system will rarely produce enough excess electricity to fully utilize a large battery.
3. Misconception: You can use stored power in winter
This statement is also among the common misconceptions about power storage and photovoltaic systems. The storage units currently available for private consumers are generally called time-of-day storage units–not seasonal storage units. They allow the surplus electricity generated during the day to be used in the evening, at night, and the next morning. In other words, when the sun isn’t shining. After that, solar power production starts again.
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4. Misconception: A power storage unit saves money
This statement is not universally true either. Battery storage units are still very costly. Money can only be saved if the total price advantage over feeding the surplus electricity into the grid over the estimated lifespan is higher than the purchase price of the storage unit. In short, if the savings exceed the cost, it’s worth it. However, the rather complex calculation also involves factors such as electricity demand, the amount of solar power produced, the electricity price and its development, and the expected lifespan.
5. Misconception: With storage, you’re independent from the grid
This is another typical misconception about power storage. PV operators still rely on the technical connection to the public power grid, even with storage. If there’s a power outage, the PV system won’t supply electricity. Nor will energy flow from the storage unit unless the operator has previously invested in an emergency or backup power system. These devices cost between 500 and 2,000 euros.