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Use the energy from your balcony power plant yourself instead of giving it away!
Four variants in focus for the calculation: A 2 kWp balcony power plant is increasingly becoming the standard in Germany – but how can you get the maximum out of it? A comparison of four variants shows, based on hard numbers, that heat can be essential even in this segment.
Balcony power plants are enjoying growing popularity. The reasons for this are diverse: a certain level of independence from rising energy prices, increasingly affordable components, and easy installation. Another major advantage is that with an inverter output of 800 W, no approval from the grid operator is required. Nevertheless, it often remains unclear how much energy can actually be used and what potential these small systems truly offer.
Many balcony power systems are installed in apartment buildings. At times when electricity consumption is highest—during the morning and evening—the yield is comparatively low. During the day, when electricity production is at its peak, the energy often remains unused and is fed into the public grid without compensation. This may delight the utility companies, but it brings no benefit to the consumer. There is significant untapped potential in making better use of self-generated photovoltaic energy.
To illustrate this potential, we examined the efficiency and self-consumption of balcony power plants using four example scenarios. We assume a two-person household in Konstanz (Baden-Württemberg) with a 120-liter hot water tank equipped with a 3 kW heating element. The calculation is based on a daily hot water consumption of 100 liters. For electricity usage, we use an hourly load profile for a couple aged 30 to 65, both employed outside the home. The household consumes 2,126 kWh of electricity per year for regular household appliances, excluding hot water production. An additional 2,287 kWh/year is assumed for hot water heating.
Based on these assumptions, several variants of a balcony power plant compliant with German regulations were calculated. The system uses an 800 W inverter and 2 kWp of module capacity. For scenarios including a battery, a 2 kWh storage unit is simulated—complete packages are offered, for example, by Zendure. The PV modules are mounted at a 30° angle from the balcony railing (i.e., a 60° tilt) and oriented southeast. The scenarios include a balcony power plant without battery storage, one with optimized heat generation using surplus electricity, one with battery storage, and a fully combined variant with both heat generation and a battery. Heat generation is controlled by the stepless Photovoltaic Power Manager AC•THOR, which directs surplus energy from the balcony power plant specifically toward hot water production.
Why this system size was chosen
Balcony power plants are often mistakenly assumed to fall into the module output category of up to 800 W, sometimes up to 1,200 W. However, a query in the German Market Master Data Register paints a different picture and explains why this system size was selected. The data is based on a query from July 30, 2025. Of the 1,056,938 balcony power plants installed and registered in Germany, more than half—specifically 548,128 systems—have an installed module capacity between 801 and 2,000 W. The maximum yield of a balcony power plant is achieved with 2 kWp of module power and an inverter output of 800 W. As of the end of July 2025, there were 61,921 balcony power plants with exactly 2,000 W installed in Germany. In general, system sizes are trending upward, as PV modules have become extremely inexpensive compared to the other components.
Scenario 1: Pure use of the balcony power plant’s PV energy without battery storage
In this scenario, 2 kWp photovoltaic modules and an 800 W inverter are simulated without any battery storage. The annual yield of the balcony power plant amounts to 1,719 kWh. The evaluation clearly shows that in a two-person household, 1,031 kWh of this solar energy remain unused and are fed into the public grid without any financial benefit for the owner. In this variant, only 688 kWh generated by the balcony system are used directly in the household, including occasional electric hot water heating. This low self-consumption rate is due to the system’s orientation and the residents’ absence during peak production times. Over the year, only 688 kWh of grid electricity are saved, while 1,031 kWh are essentially “given away” to the grid operator.
A nice little bonus for electricity providers—considering there are more than 1 million balcony power plants in Germany—but far less advantageous for consumers (as of July 2025)!
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| Table 1: Balcony power plant with 2 kWp without battery storage, with occasional hot water heating | |
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| Table 1: Balcony power plant with 2 kWp without battery storage, with occasional hot water heatingAC energy production | 1,719 kWh/year |
| Table 1: Balcony power plant with 2 kWp without battery storage, with occasional hot water heatingFeed-in to the grid | 1,031 kWh/year |
| Table 1: Balcony power plant with 2 kWp without battery storage, with occasional hot water heatingGrid consumption | 3,725 kWh/year |
| Table 1: Balcony power plant with 2 kWp without battery storage, with occasional hot water heatingDirect consumption of the heater from the balcony power plant | 158 kWh/year |
| Table 1: Balcony power plant with 2 kWp without battery storage, with occasional hot water heatingSolar coverage of hot water demand | 7% |
Scenario 2: Using surplus energy from the balcony power plant for hot water heating
In the second variant, the balcony power plant is equipped with a steplessly adjustable power controller that measures surplus energy from a meter at the grid feed-in point. By monitoring the surplus, a significant amount of energy can be transferred to the hot water tank via a heating element—even with a small balcony system. This allows the solar coverage of hot water to be increased and the generated energy of the balcony power plant to be used efficiently. One solution for this is the EcoTracker from everHome. This energy meter can be installed by the end-user without professional assistance, as it simply clips onto the existing meter without interfering with the electrical system.
A steplessly adjustable Photovoltaic Power Manager, such as the AC•THOR from my-PV, can then control the 3 kW heating element in the hot water tank to provide heat. Over the course of a year, 972 kWh from the balcony power plant are used for hot water heating. In other words, nearly 43% of the annual hot water demand for a two-person household can be covered using what would normally be surplus energy from a 2 kWp balcony power plant.
Furthermore, only about 165 kWh per year are fed into the public grid—approximately 84% less compared to the variant without stepless regulation, where excess energy is fed into the grid for free. Grid electricity consumption for household devices and lighting remains the same as if the hot water system were not used, meaning there are no additional operating costs; in fact, it can even be cost-saving. Solutions from my-PV use only the surplus PV electricity from the balcony power plant. Increasing self-consumption and energy independence is therefore very easy to achieve!
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| Table 2: Balcony power plant with 2 kWp, without battery storage, with steplessly controlled hot water heating | |
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| Table 2: Balcony power plant with 2 kWp, without battery storage, with steplessly controlled hot water heatingAC energy production | 1,719 kWh/year |
| Table 2: Balcony power plant with 2 kWp, without battery storage, with steplessly controlled hot water heatingFeed-in to the grid | 165 kWh/year |
| Table 2: Balcony power plant with 2 kWp, without battery storage, with steplessly controlled hot water heatingGrid consumption | 2,624 kWh/year |
| Table 2: Balcony power plant with 2 kWp, without battery storage, with steplessly controlled hot water heatingDirect consumption of the heater from the balcony power plant | 972 kWh/year |
| Table 2: Balcony power plant with 2 kWp, without battery storage, with steplessly controlled hot water heatingSolar coverage of hot water demand | 47% |
Scenario 3: Balcony power plant with battery storage
For many balcony power plant owners, using a battery storage system—available in various sizes—has become almost obligatory. The less self-generated PV electricity is fed into the grid, the better the owner feels. A battery reduces grid feed-in and allows the energy to be stored. With a battery, the produced energy can also be used at times of the day when the balcony system is no longer generating electricity. The following calculation examines a variant with a battery but without controlled hot water heating.
For this calculation, a 2 kWh battery storage system was added while keeping the module capacity at 2 kWp. However, the stepless control for hot water heating was removed in this scenario. Even with a battery sized equal to the PV module output, 287 kWh are still fed into the grid for free—122 kWh more than in the scenario with stepless hot water heating but without a battery, where only 165 kWh were fed in.
This is a significantly better result than the 1,031 kWh fed into the grid in the scenario without battery storage, but 287 kWh are still effectively “given away.”
Compared to the previous variant (without battery, but with hot water heating), the 3 kW heating element with the AC•THOR draws 2,624 kWh from the grid. In contrast, in the battery-only scenario, 2,981 kWh must be drawn from the grid. This clearly shows that more energy can be stored in hot water than in the battery!
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| Table 3: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage, without stepless hot water heating | |
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| Table 3: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage, without stepless hot water heatingAC energy production | 1,719 kWh/year |
| Table 3: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage, without stepless hot water heatingFeed-in to the grid | 287 kWh/year |
| Table 3: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage, without stepless hot water heatingGrid consumption | 2,981 kWh/year |
| Table 3: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage, without stepless hot water heatingDirect consumption of the heater from the balcony power plant | 158 kWh/year |
| Table 3: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage, without stepless hot water heatingSolar coverage of hot water demand | 7% |
Scenario 4: Balcony power plant with battery storage and hot water heating
Now, the combination of a balcony power plant, battery storage, and stepless hot water heating is considered. This is certainly the most cost-intensive variant due to the initial investment in the battery and the additional expense for PV-powered hot water heating. The results are as follows: the battery is charged first, covering part of the household electricity consumption, and only then is surplus energy directed to hot water heating. As a result, only 11 kWh per year are fed into the grid—just 1% compared to Scenario 1 (a conventional balcony power plant).
With this configuration, the balcony power plant owner can cover 39% of their own electricity consumption and an additional 43% of their annual hot water demand.
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| Table 4: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storage | 1,719 kWh/year |
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| Table 4: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storageAC energy production | 1,719 kWh/year1,719 kWh/year |
| Table 4: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storageFeed-in to the grid | 1,719 kWh/year11 kWh/year |
| Table 4: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storageGrid consumption | 1,719 kWh/year2,499 kWh/year |
| Table 4: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storageDirect consumption of the heater from the balcony power plant | 1,719 kWh/year879 kWh/year |
| Table 4: Balcony power plant with 2 kWp, 800 W inverter with 2 kWh battery storageSolar coverage of hot water demand | 1,719 kWh/year43% |
You can only get the maximum from a balcony power plant with hot water heating!
A stepless controller, such as the AC•THOR, can use the maximum surplus power from the balcony power plant for hot water production, significantly increasing self-consumption. A battery storage system can also help store and use excess energy when needed. The combination of battery storage and stepless hot water control further boosts efficiency: in the simulation, only 11 kWh are fed into the grid, while impressive coverage levels are achieved for both hot water heating and household electricity—fulfilling the main goal of a balcony power plant.
Balcony power plants offer many advantages—using stepless hot water heating, owners can extract the absolute maximum from their system.
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AC•THOR
the Photovoltaic Power Manager
Simple & efficient: AC•THOR controls electrical heat sources depending on the availability of PV energy and heat demand. And that for both hot water, as well as for space heating.
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