Hot Water Solar Panels: Costs, Pros, and Cons (2023)

Hot Water Solar Panels: Costs, Pros, and Cons (2023)

Solar panels for hot water capture sunlight and convert it into usable heat. In principle, only the collector, piping system, and hot water tank are required. This article will teach you what solar thermal collectors are, how they work, the advantages and disadvantages of this system for heating water, and how much it costs.

What do hot water solar panels mean?

Solar panels for hot water are used for the solar thermal system. They absorb solar energy and use it to heat water in your home. The technology is mainly used to heat domestic water and support heating systems. Solar panels for hot water are often installed on the roof of a building or in an open space to ensure maximum exposure to sunlight.

There are two main types of solar panels for hot water:

  • Flat-plate collectors consist of a flat, absorbent-coated plate surrounded by a transparent cover.
  • Evacuated Tube Collectors: These consist of several evacuated glass tubes to minimize heat loss.

Bifacial solar panels are an environmentally friendly and sustainable solution that reduces energy consumption and greenhouse gas emissions as they use renewable energy. Don’t confuse them with solar panels for electricity generation (another type of solar panel), which convert sunlight into electricity.

How do solar panels for hot water work?

Solar panels for hot water work using the sun’s infrared spectrum.

  • With flat panel collectors, solar energy is absorbed by the panels and transferred to the underlying ductwork, which is filled with a heat transfer fluid. This liquid is heated and transported through a pipe system to a heat accumulator, which transfers heat to the process water.
  • With evacuated tube collectors, there is an absorber in each tube that absorbs solar energy and transfers it to the heat transfer fluid it contains. The heated liquid is then sent to a heat accumulator to heat domestic water.

Once the heat transfer fluid has heated the water in the tank, it flows back to the solar panels, where it absorbs heat again. The liquid thus circulates in a constant cycle.

Pros and Cons of Hot Water Solar Panels


  • Environmentally Friendly: Using solar energy is an environmentally friendly energy source, and most importantly, it is a CO2-free alternative to fossil energy supplies such as oil or natural gas.
  • Cost Savings: Installing solar panels for hot water can save much money in the long run because solar power is free. Therefore, no fuel costs such as oil, gas, pellets, or electricity exist.
  • Independence: With solar panels for hot water, you will be less dependent on energy suppliers and rising prices.
  • Appreciation: A solar system can increase the value of your home, and it can be a selling point if you want to sell your property.
  • Long service life: The service life of solar collectors used to heat domestic water is typically 30 years.


  • Weather Dependency: The hot water efficiency of solar panels depends on solar radiation. The system’s efficiency will be greatly reduced on cloudy or rainy days.
  • High investment cost: Installing solar panels for hot water requires a slightly higher investment cost. Therefore, solar thermal systems only pay for themselves after 15 to 20 years.
  • Low production in winter: Solar panels generate the most heat in summer. In winter, yields are significantly lower.
  • Summer waste heat: Unfortunately, waste heat cannot be stored or sold like photovoltaic systems. A lot of unused heat is generated, especially in summer.

The cost of hot water solar panels

A solar thermal system for a single-family house costs between 4,000 and 6,000 euros. Hot water solar panels cost a little under €1,000 to €2,500, hot water tanks cost between €1,000 and €1,500, and plumbing and installation costs around €1,500 to €2,000.

Cost center Expense
Solar panels EUR 1,000 – EUR 2,500
Hot water tank (260 – 340 liters) EUR 1,500 – EUR 1,500
Piping and fittings EUR 1,500 – EUR 2,000
Total solar thermal cost EUR 4,000 – EUR 6,000

Hot Water Solar Panel Subsidies

There are various state and local subsidies for installing solar panels for hot water. Funding amounts vary by location and type of facility. Therefore, you must determine whether the Special Funding Program is right for you from the responsible city or region.

One financing option is KfW Bank. It offers low-interest financing as part of the 260/261 program for new buildings. Get a repayment subsidy of up to 5% if you reach efficiency level 40.

As part of the BEG (Federal Fund for Efficient Buildings), the BAFA (Federal Office of Economics and Export Control) also supports installing solar systems for hot water. A subsidy of up to 25% of the acquisition cost is available if a solar thermal system is used as a retrofit measure in a home at least five years old. Even up to 35% is possible in combination with a heat pump.

Hot Water Solar Panels: Tips and Tricks

You can use a few tips and tricks when installing solar panels for hot water. First, ensure your roof is oriented for optimal sun exposure. The system should also be sized according to your needs to ensure optimum efficiency. Regular solar panel maintenance and system cleaning are also important to ensure a long service life and optimum efficiency. Combinations with conventional heating systems or heat pumps also help ensure energy supply on sunny days.

Roof facing

Solar panels should be installed on south-facing roofs, where they get the most possible heat. A southeast or southwest orientation also yields good yields. A roof slope of 30 to 60 degrees is ideal. Also, shadows from nearby buildings, trees, skylights, and chimneys should not fall on the solar panels. Also note that the sun does not only move during the day but also throughout the year, so, for example, shadows get longer in winter.


The solar system should be sized to suit your individual hot water needs. The system can cover the full range of summer needs with the right design. In winter, the house’s main heating system had to help. An average of 60% coverage of requirements can be achieved.

You can calculate the optimal size yourself as follows:

Each person in the household needs about 50 liters of hot water. A solar panel area of 0.8 to 1.2 square meters is sufficient. Also, consider the orientation and spacing of the roof and the choice of solar panels. Flat plate collectors are slightly more efficient than tube collectors. The capacity of the hot water tank should be about 70-100 liters per person. Potable water storage tanks of 260 to 340 liters are common in single-family homes.

Maintenance and cleaning

Solar panels last 30 years or more. They should be maintained and cleaned regularly. Maintenance should be performed approximately every two years. Check collectors, solar fluid, connections, piping, and insulation. The average fee is 100 euros.

You can clean the solar panels yourself if they are easily accessible. If you must climb extra, hiring a professional is best. To clean, use a soft sponge or brush, preferably only warm water or mild detergent, to avoid damaging the surface of the solar panel. It’s easiest to clean right after rain because the dirt has already soaked through.

Combination with other heating systems

Solar panels cannot fully meet a home’s year-round hot water needs. Therefore, a combination with another heating system makes sense. A heat pump is especially recommended here, as it is also suitable for heating.

A heat pump uses energy from the environment to bring the water to the desired temperature, supporting a solar system when needed. By combining these two technologies, the efficiency and reliability of the system can be increased, ensuring a constant supply of hot water even when solar radiation is low.

In conclusion 

Solar panels for hot water are a smart and environmentally friendly investment for homeowners who want to save money in the long run while reducing their ecological footprint. The acquisition costs of 4,000 and 6,000 euros may seem a bit high initially. However, the savings in hot water costs can be significant in the long run. In addition, subsidies and subsidies can further reduce the cost of acquisition.

If you purchase a solar heating system for hot water, ensure it is carefully planned and installed. A heat pump can also increase the efficiency of the system. Please complete our form if you are interested in your solar thermal system. We’ll then connect you with up to five qualified companies in your area – free of charge and without obligation. The solar pump kit harnesses renewable energy to efficiently power water pumps, offering a sustainable solution for irrigation, livestock watering, and off-grid water supply needs.