Retrofitting energy storage: What you need to pay attention to
%25203%2520(1).webp)
Stefano Fonseca is an energy and environment engineer with over six years of experience in technical building equipment (TGA). He combines technical expertise with a passion for understandable communication. For more than five years, he has been writing as a freelance editor about renewable energy and sustainable living, in particular about photovoltaics and heat pumps.
Without an energy storage system, the majority of the PV power generated flows into the grid. However, self-consumption is becoming more and more worthwhile due to rising electricity prices and falling feed-in tariffs. For this reason, energy storage systems are being retrofitted more and more frequently. Here you can find out everything you need to know when upgrading.
Can you retrofit an energy storage system?
You can easily retrofit a power storage unit. Most photovoltaic systems can also be supplemented with a storage system years after installation. This is particularly easy with AC-coupled systems, as they function independently of the existing inverter.
Which energy storage systems are suitable for retrofitting?
AC-coupled energy storage systems are particularly suitable for retrofitting. These storage systems work independently of the existing inverter and are therefore particularly easy to retrofit. They convert the direct current of the battery into alternating current before it is fed into the home network. This makes them flexible, even with older PV systems.
DC-coupled storage systems, on the other hand, are better suited for new systems, as they require a direct connection to the solar modules. Hybrid solutions are also possible, but often only make sense if you also replace the inverter.
When is it worthwhile to retrofit an energy storage system?
Upgrading an energy storage system is worthwhile starting at an electricity price of around 30 cents per kilowatt hour. Retrofitting is particularly worthwhile when electricity consumption is high, such as a heat pump or an electric car. Investments with an expiring feed-in tariff also benefit, as self-consumption is economically more attractive than the low remuneration.
Without storage, you usually only use 20 to 30 percent of your solar power yourself. With storage, self-consumption rises to up to 70 percent. This saves running costs, makes you more independent of the electricity market and increases the degree of self-sufficiency. Retrofitting is particularly worthwhile if the costs are below 800 euros per kWh.
How much does it cost to retrofit an energy storage system?
Retrofitting an energy storage system costs a total of between 5,000 and 10,000 euros.
On average, you pay around 600 to 1,200 euros per kilowatt hour of storage capacity. Small storage systems with around 5 kWh cost around 5,000 to 6,000 euros. For larger systems with 8 to 10 kWh, you can expect 7,000 to 10,000 euros.
Additional costs may arise for installation, new meters or modifications to the electrical distribution system. Funding programs can significantly reduce investment.
What funding is available for retrofitting?
There are currently no direct subsidies nationwide for retrofitting an electricity storage system, but there are low-interest loans through the KfW 270 program. In addition, many cities and federal states offer their own funding programs with direct subsidies. Some municipalities also provide subsidies or climate bonuses.
How does the retrofitting of an energy storage system work?
The retrofitting of an energy storage system is carried out in several clear steps and should always be accompanied by a specialist company.
- System test: A specialist company will check your existing PV system for compatibility, power reserves and technical requirements.
- Analyze load profile: Your power consumption is evaluated and Determine the appropriate memory size. What is important is how much electricity you use and when.
- Get advice & offer: Based on the analysis, you will receive a recommendation for the appropriate storage system, including a cost estimate.
- Check funding opportunities: Before installation, you should apply for regional funding programs or a KfW loan, if available.
- Prepare for installation: The electrician clarifies whether there is space in the technical room, whether new meters are required and how to connect the storage system.
- Assembly and connection: The energy storage system is installed, wired and connected to the existing PV system. AC systems are usually particularly easy to retrofit.
- Registration and start-up: The memory is reported to the network operator and officially put into operation. If necessary, the market master data register will also be updated.
- System test and briefing: After a successful functional test, you will receive instructions on how to operate and use the app to monitor the memory.
A well-planned process ensures that your storage system works efficiently and that you get the most out of your PV system.
What do you have to pay attention to when retrofitting?
When retrofitting an energy storage system, you must pay attention to several technical and economic factors so that the system works reliably and economically.
- Check the compatibility of the PV system: Not every system can be retrofitted without adjustment. In particular, the inverter and the cabling must harmonize with the storage system.
- Choose the correct storage type: AC storage systems are particularly suitable for retrofitting, as they function independently of the existing inverter. DC and hybrid solutions are usually only worthwhile if the plant is completely renovated.
- Size the storage size accordingly: The memory should not be too big or too small. A size that covers daily consumption is ideal. An analysis of your load profile helps with the selection.
- Clarify space requirements and installation location: An energy storage system requires a dry, frost-free room with sufficient space. A cellar, laundry room or technical room are typical.
- Observe charging and discharging performance: The capacity of the storage system determines how quickly energy can be charged or withdrawn. Make sure the values are adequate, especially with heavy loads.
- Optionally include emergency power capability: If you want to be powered even in the event of a power failure, you need a storage system with emergency power function. This requires additional technology and higher costs.
- Have the network connection and meter checked: Depending on the network operator, a meter exchange or a second meter may be necessary. This should be clarified early on.
- Apply for funding programs before installation: State or regional funding must usually be applied for before the contract is concluded.
Conclusion: Who is retrofitting really worthwhile for?
Retrofitting an energy storage system is particularly worthwhile for homeowners with a high level of self-consumption, such as a heat pump or electric car. Even with older PV systems without a feed-in tariff or with an expiring feed-in tariff, a storage system has clear advantages, as self-consumption makes more economic sense than feeding in the grid. If the electricity price exceeds 30 cents per kilowatt hour and the investment costs remain below 800 euros per kWh, the retrofit can also quickly pay off financially.
The new standard for installers and energy consultants
Are you installing heating systems, PV systems, battery storage systems or wallboxes? With autarc, you can carry out acquisition, planning, promotion, maintenance and customer communication in one software. Digitize your processes and make your company fit for the future. Try it now for free for 14 days!