Three PV modules cover 50% of hot water needs

2026 . 02 . 27

Is there still space available on your balcony alongside your balcony power plant? With just a few additional modules, you can generate significant amounts of hot water – using SOL•THOR.

In Germany and Austria, the output of balcony power plants that do not require registration or approval is limited to 800 watts. This output is already achievable with just two solar modules. For those with more space available, it has so far been possible to install additional balcony power plant modules with microinverters and standard plugs. However, this required undergoing complex approval processes for a grid-connected system. With the new DC power manager, SOL•THOR, which my-PV will launch in the first quarter of 2025, approval requirements are eliminated – because it’s an autonomous solution.

What is a balcony power plant?
Balcony power plants are simple to implement and are gaining popularity. Their goal is to allow private individuals to operate small photovoltaic systems without cumbersome approval processes. A microinverter converts the direct current (DC) from the module directly into usable alternating current (AC), which can then be fed into the household electrical system via a standard outlet. Installation and operation are straightforward, the cost savings are easy to calculate, and the investment – compared to a larger PV system – is very manageable. There is no complicated registration or approval required, making it an easy way to reduce electricity costs – even in apartments.

What to do if there’s extra space on the balcony?
If you want to utilize the entire available area of your balcony railing for photovoltaics, you still don’t have to go through the complicated approval process for a grid-connected system. The solution: Use the remaining space with standard modules to produce hot water with photovoltaics via an electric boiler! (Image: Balcony setup with plug-and-play PV modules featuring microinverters (grey) and standard photovoltaic modules (green) for water heating.)

Maximizing balcony energy production
This innovative approach allows larger balcony railings to be fully utilized for energy generation. The balcony power plant can continue to support household appliances and alleviate traditional electricity consumption. Additionally, for water heating, it is now possible to install standard photovoltaic modules with MC4 connectors either as a supplement or a complete alternative. Using a standalone PV heat control device, a conventional electric boiler can be transformed into a solar energy storage unit for daytime use.

Affordable and flexible solar modules
Standard photovoltaic modules (with MC4 connectors) are 50% more affordable than balcony power plant modules equipped with microinverters and Schuko plugs.

To bridge the gap between small balcony power plants with two modules and grid-connected PV systems typically exceeding 5 kWp, my-PV is launching the SOL•THOR in early 2025. This autonomous PV heat control device directly utilizes DC power from modules for water heating, bypassing the need for inverters.

Key features of SOL•THOR

• Flexible module capacity: Supports between 1 and 10 modules, depending on the available space and energy requirements.
• Off-grid operation: The PV modules are not connected to the public grid, eliminating the need for approval.
• Wide power range: The stepless control range from 0 to 3.6 kW is compatible with all common electric boilers.
• Energy efficiency: Ensures minimum temperature maintenance even during low PV production, guaranteeing comfort at all times.

This solution enables households to harness solar energy for heating – efficiently, affordably, and without regulatory hurdles.

What can be expected from such a system?
Let’s consider an apartment in Central Europe where two standard photovoltaic modules, each with 450 Wp, are combined with the SOL•THOR to provide hot water. The modules are south-facing and mounted vertically on the balcony railing. They power an electric boiler with a 120-liter capacity, equipped with a 2 kW heating element. The apartment is home to two people who use approximately 100 liters of hot water daily.

Using a reputable dynamic simulation program, it can be calculated that such a system can cover 34% of the annual hot water demand for these two residents. This reduces the grid electricity required for the boiler by one-third.

Is it economical?
Yes! This one-third reduction corresponds to nearly 700 kWh of energy that no longer needs to be purchased from the electricity provider. At an average electricity price of €0.35/kWh, this results in annual savings of €245. Additionally, many residential buildings already come equipped with a hot water storage tank and heating element, which can be easily adapted for PV heating.

When the annual savings are compared to the investment, assuming an end-user price of €100 per module (including VAT) and €830 for the SOL•THOR (including VAT), plus a small additional cost for wiring and accessories, the payback period is just 4 to 5 years. In times of increasing energy supply uncertainties and volatile market prices, this represents an exceptionally simple solution for greater independence in heat supply. Moreover, the SOL•THOR operates even during power outages, making it a truly off-grid solution.

If additional space is available, a system with three modules can achieve 50% of the hot water demand in the same example. This also reduces the payback period to just three years!

Learn more about the SOL•THOR on our website.