FAQ

There is no single answer; it depends on your needs (daily hot water demand), the technology you want to use (more sophisticated and efficient technologies, such as forced-circulation systems with evacuated-tube collectors, are more expensive than simpler types), and also on whether the system is being installed in a new home or an existing one.
But what matters most of all is that a properly sized solar system will save you far more over time than it cost to install. Furthermore, a significant portion of the initial cost could be covered by incentives.

The cost of the panels alone depends on their type and size. However, the cost of the panels is only one part—albeit a significant one—of the total cost of a solar thermal system. Therefore, it is generally a good idea to evaluate the cost of the entire system, including installation (see FAQ #1).

Cost-effectiveness depends on many factors: installation location, usage, exposure, alternative heat sources, and more. A solar thermal panel is always cost-effective as long as it is used with a certain degree of consistency. Long periods of inactivity, especially in the spring and summer, limit its cost-effectiveness. For each specific case, Pleion can run simulations to assess, within a particular context, which system is the most cost-effective.

There are various types of solar thermal panels that differ in how they operate (direct flow, natural circulation, forced circulation) and in their construction (flat-plate glass, evacuated-tube, etc.).
Each type has its own purpose and is suited to different situations and needs.
However, we can say that the highest performance is generally achieved with evacuated-tube collectors, which are capable of maintaining high performance even during the coldest season.

During the winter, the number of hours of sunshine decreases, and consequently, the amount of energy the sun radiates daily onto the surface of our solar panels also decreases. In addition, low temperatures make operating a solar system more challenging in the winter.
However, there is a technology—vacuum-tube panels for forced-circulation systems—that can operate efficiently even in very cold weather, making the most of solar radiation even when it is reduced.

The amount of water supplied each day varies from day to day and depends on the season and weather conditions. In fact, a solar water heating system is generally not the sole source of hot water but is supplemented by a conventional system (such as a boiler or heat pump) that ensures a supply of hot water when there is insufficient sunlight. In general, a system properly sized to meet demand provides between 50% and 75% of the hot water needed for a home on an annual basis and ensures nearly complete independence during the summer months.

Depending on conditions, the installation site, the panels’ orientation, and other factors, a well-designed system can provide between 450 and 800 kWh/year per square meter of collector surface area, which corresponds to an equal amount of usable energy savings. To convert energy savings into financial savings, it is necessary to know the associated energy source, as well as the efficiency of the existing conventional heat generator.

If the system has been properly sized and correctly installed, you will save far more over time than you spent on it.
The savings will be even more significant in situations where the associated conventional fuel source is diesel or LPG.

It depends on the specifications and size of the system, which, in turn, must be sized and selected based on the user’s needs and requirements. That’s why PLEION offers a wide range of solar kits in its catalog to meet different needs and at various price points.

Here, too, there are many different solutions that vary in size, features, and price.
A natural-circulation system is simpler and more economical than a forced-circulation system.
This solution is particularly well-suited to mild climates.

Stagnation is the condition in which the solar system stops functioning and begins to boil because it receives more energy than it can transfer to the user or the storage system.
If stagnation occurs sporadically, it is not a problem. If, however, it occurs frequently during the summer, this may result in the need for frequent maintenance to replace the antifreeze circulating in the panels. This is the case, for example, with a system designed to contribute to space heating in the winter and which is consequently oversized in the summer.
An effective solution is possible when there is an outdoor pool, into which the excess heat can be diverted, thereby also providing pleasant heating for the pool.
If there is no pool, Pleion has patented the ECLIPSE system, which is compatible with its entire line of vacuum-tube panels. This system automatically shades the solar panels when the storage tank can no longer accept energy or when the panels exceed a defined temperature threshold.

In direct-flow panels, such as EGO and EGO PRIME, domestic hot water is heated directly.
In FREE-type natural-circulation panels, the fluid circulating through the solar panels is a mixture of water and glycol, which, in turn, heats the domestic hot water.
In forced-circulation panels as well, a glycol-water mixture circulates, transporting solar heat from the panels to a storage tank, which may contain domestic hot water or “technical” water (i.e., water from the heating circuit). In the latter case, the stored heat can be used both for space heating (especially in combination with a low-temperature radiant panel system) and, via an additional heat exchanger, for producing domestic hot water.

Important! The water heated by the panels can reach very high temperatures, especially in the summer. It is always recommended to install a thermostatic mixing valve to prevent scalding.

Solar thermal panels consist of a collector surface—known as an absorber—with selective properties (in practice, it is particularly effective at “capturing” solar radiation and retaining it) and which, when exposed to sunlight, transfers heat by conduction to a fluid circulating in dedicated circuits, which then transfers it to domestic hot water or, in some cases, to the water in the heating system.
Direct-flow panels, such as EGO and EGO PRIME, on the other hand, store domestic hot water directly inside the panel, where it is heated directly by the sun. When a faucet is turned on, the hot water inside the panel flows through the pipes to the user and is replaced in the panel by new, cold domestic water, which is then heated.
In all cases, there is a transparent cover and insulating material that reduce heat loss from the solar panels, ensuring that most of the energy is transferred to the fluid and as little as possible is lost to the outside.

It depends on the specific needs and the location. However, we can say that the most common system for providing hot water to a family of 3–4 people is one with a 300-liter water heater and 2 solar panels totaling 4–5 m².