The on-roof photovoltaic system is the standard module attachment on the house roof. The on-roof installation can be used flexibly as a retrofit for existing and new buildings.
Furthermore, there are suitable mounting solar panel systems for every roof covering. Due to the high standardization of the on-roof installation, the acquisition costs are considered moderate, which is why on-roof systems are very popular with PV system owners.
But how well does rooftop photovoltaics fare compared to possible alternatives? What special features must be considered when installing on the roof, and how much does a PV system on the roof cost?
Photovoltaics: In-Roof or On-Roof?
The two installation variants are completely different concepts: in the case of the on-roof system, the functionality of the energy production is the top priority. In contrast, the in-roof system is chosen more for aesthetic reasons.
Rooftop photovoltaics are mainly used for existing houses. This is advantageous because most single-family homes are planned without considering a future PV system.
The on-roof system can be retrofitted at any time as long as the roof is not renovated and will remain watertight for at least 20 to 30 years. On-roof modules can also be used in a new building without any problems.
In contrast to on-roof photovoltaics, in-roof photovoltaics are integrated directly into the roof and act as separate roof skin.
At the point where in-roof modules are installed, there is no tile roofing.
This saves on covering material and leads to a more elegant roof appearance.
The roof-integrated PV system requires much planning effort and special knowledge from the solar technician or roofer.
On the other hand, installing the on-roof PV system is easy to carry out (by a specialist). With an intact house roof, the installation costs for on-roof photovoltaics are 20 to 30 percent, significantly lower than for in-roof PV because there is no time-consuming dismantling of the roof covering.
A big advantage of the on-roof solar system is the good rear ventilation of the PV modules. These are fixed at about 10 cm from the roof tiles. As a result, there is good air circulation behind the modules, also referred to as the rear ventilation of the solar modules.
This constant draft brings a cooling capacity that significantly impacts performance, efficiency, and photovoltaic yield. On the other hand, in-roof photovoltaics can only guarantee a small amount of rear ventilation, leading to yield losses of up to 10 percent per year.
Installation of the PV system on the roof: this must be taken into account
When it comes to on-roof installation, there are two different types of roof: the pitched roof and the flat roof.
The pitched or sloping roof is well suited for photovoltaics because it usually has a favorable inclination angle (30 to 50°) for generating electricity. The solar modules can therefore be mounted flat or parallel to the roof. This enables the best use of space.
There are different types of pitched roofs, such as the pitched roof, the hipped roof, or the pent roof. No matter what type, a fixation or screw connection to the roof truss, more precisely to the rafters, is always required during assembly.
The on-roof system offers the wind forces, wind suction, and pressure a large attack surface. Therefore, the on-roof installation must be sufficiently stable to withstand strong wind gusts during a storm. To ensure this, the manufacturer of the PV substructure has specific requirements:
Aluminum or stainless steel roof hooks are used for anchoring to the rafters.
The distance between individual roof hooks must not be too large (usually max. 1.6 m)
Special screws, flat head screws with a length of at least 100 mm, are used for the screw connection.
When installing the solar panel system, the adjustable roof hooks are attached first. One or two roof tiles must first be removed to make the counter battens visible.
The roof anchor is put on and fastened with two screws in the rafter. The tile must be adjusted using an angle grinder to be used again despite the annoying roof hook, and the roof is sealed.
If the roof hooks are used, they are connected with aluminum rails. Usually, the tile roof is not perfectly straight or even. The roof’s inequality is compensated with height-adjustable roof hooks, so a uniform and aesthetic module field is created later.
If the solar modules are mounted upright, two metal rails are required to fasten each module row.
In the case of transverse installation, further rails are required in the vertical roof alignment. This costs more material and assembly time, so it is only done in exceptional cases.
Once the metal frame has been assembled, the modules are laid. They are wired together and then attached to the rails with four module clamps.
A few things change with on-roof mounting on a flat roof: the modules are not placed flat but are elevated on a special mounting system. Flat roof photovoltaics can therefore be used flexibly and often only be fixed by ballast, i.e., without penetrating the roof.
Cost of Rooftop PV System
How much are solar panels? A rooftop photovoltaic system costs between 1,500 and 1,900 euros per kW. The electricity storage costs about 1,000 euros per kWh extra. A typical ten kWp PV system with storage results in an average price of around 26,000 euros.
The price per power unit decreases the larger the PV system becomes. It is advisable to cover the entire roof with PV modules. Using several roof sides for electricity production can also make sense depending on the local conditions.
Is a PV System on the Roof Worth it?
Although the costs of rooftop systems increased in 2022 and 2023, as the PV price development shows, the conditions are currently more favorable than they have been for a long time. Since the beginning of 2023, no VAT has been charged on purchasing the PV system. It is also no longer an applicable Obligation to tax profits from the operation of rooftop photovoltaics.
Due to high electricity costs, using your solar power and saving money is worthwhile. Overall, photovoltaics is currently profitable from a financial and ecological point of view.
Would you like to purchase your photovoltaic system in a complete package with on-roof installation? Then use the form below to receive offers from suitable specialist companies in your area.
