Can photovoltaics be integrated or retrofitted on rooftops?

There are two types of photovoltaic roofs:

 

The retrofitted PV system is mounted on the roof of the house.

Roof-integrated photovoltaics, whereby in-roof modules or solar tiles replace the roof covering.

On-roof installation

Normally, PV modules are mounted on the tiled roof or roofing. The solar system thus functions as a separate unit, independent of the roof covering. Since most photovoltaic systems are placed on existing roofs, on-roof installation is particularly practical and inexpensive.

 

Rooftop photovoltaics are well-suited for existing and new buildings and are the most popular option for single-family homes.

 

in-roof installation With in-roof installation, PV modules are inserted directly into the roof construction to generate energy and seal the roof.

 

Compared to on-roof installation, in-roof systems offer aesthetic advantages, lower weight, wind resistance, less noise, and good self-cleaning.

 

In-roof photovoltaics are suitable for listed buildings and are particularly worthwhile when the roof is renewed, or a new building is built.

 

The performance corresponds to conventional rooftop modules, with 30 to 40 years of durability.

 

solar roof tiles

Solar roof tiles are a combination of roof tiles and panels that convert solar energy into electricity while protecting against the elements. Compared to on-roof photovoltaics, they are integrated into the roof and offer an attractive appearance.

 

Solar roof tiles vary in size, material, and shape and adapt to different roof coverings.

 

They are durable and environmentally friendly but more expensive and less efficient than traditional PV systems. Installation is more complex, and there is a higher risk of failure due to the numerous small modules.

How much does photovoltaics on the roof cost?

The cost of solar panels varies depending on size and performance. On average, a PV system without storage costs around 1,650 euros per kilowatt peak (kWp). The following applies the larger the system, the lower the specific costs per service unit.

 

A 5 kWp PV system costs around 1,700 euros, while a 15 kWp PV system is around 1,600 euros per kWp.

 

A 10 kW complete photovoltaic system, including installation, costs an average of 16,500 euros, although this price does not include an electricity storage unit. For the additional photovoltaic storage, you must reckon with costs of around 800 to 1,200 euros per kilowatt hour (kWh) of lithium leisure battery capacity, around 1,000 euros per kWh on average.

 

A solar roof without tiles, on the other hand, is more expensive to buy. In-roof photovoltaics cost about 20 percent more than a normal on-roof system. Additional costs of over 100 percent must be expected when using solar roof tiles because the technology is not yet widespread.

 

This variant of the PV roof is not worthwhile for existing houses. In the case of a new building, savings can be made on the roofing material, which reduces the overall price somewhat.

 

Funding for the photovoltaic roof

PV systems are funded by the Renewable Energy Sources Act (EEG). Excess solar power is reimbursed (see feed-in tariff).

 

If there is insufficient equity for the purchase, a photovoltaic loan can be used. The KfW bank from the federal government offers a (comparatively) cheap loan for purchasing a PV roof and electricity storage.

 

Solar systems are given preferential tax treatment. This type of funding is intended to further accelerate the expansion of renewable energies. A new law was passed so that a VAT rate of 0 percent is charged when purchasing a photovoltaic system.

There are also numerous regional funding programs for PV systems and power storage or wall boxes. These are often limited in time and to a fixed number of funding applications. The federal state or the district determines many subsidies.

 

Is a photovoltaic system on the roof worth it?

 

Photovoltaic systems on the roof are worthwhile both financially and ecologically. Most PV system operators pursue several goals when setting up the solar system:

 

Reduce electricity costs

Protection against rising energy costs

(higher) independence from the electricity company

cheap electricity for charging the electric car

advance the energy transition

Reduce CO₂ footprint

Invest money in photovoltaics worthwhile

 

But the conditions for the feed-in also improved again in mid-2022: The feed-in tariff rose by around 31% to 8.2 cents per kWh (up to 10 kW), which increases the yield of a PV system.

 

The prices for solar components and complete photovoltaic systems have increased by 15 to 30 percent since 2020. Nevertheless, the conditions for purchasing a solar roof can still be rated positively.

 

One factor should not be ignored: Since the beginning of 2023, there has been no obligation to tax profits from the operation of the PV system. In addition, no VAT is due on the purchase.

 

Bringing PV modules to the roof: this is how it works

 

Before the photovoltaic installation can begin, the process is first meticulously planned. Depending on

the type of roof, a suitable mounting system is required. A PV substructure is used for the usual PV system on the pitched roof.

 

This consists of a metal frame, which is screwed to the counter battens and the rafters with the help of roof hooks.

 

The solar modules are then attached to the aluminum rails using module clamps and electrically connected.

 

With the in-roof variant, the modules are usually placed directly on the roof battens or planks and anchored using mounting brackets. Some mounting systems rely on PV modules with special frames suitable for sealing, while others require an additional water-draining protective plate (usually corrugated iron) under the modules.

 

High safety measures must be observed during installation. Scaffolding is always required. To bring the PV modules onto the roof, several people lift them from floor to floor.

 

Some specialist companies use a lifting platform or a roofer’s lift for the process, which greatly reduces the physical exertion of the work. Starting from the scaffolding, two craftsmen bring each solar module to the right place on the roof, wire it up and fix it.

 

Overall, installing a photovoltaic system on the roof can take a few days to two weeks, depending on the size and complexity of the system. It is advisable to rely on a professional company to install and maintain the system to ensure optimal results and the long life of the PV system.

 

Alternatives to the photovoltaic roof

 

A solar system does not necessarily have to be mounted on the roof of the house but can also be installed on outbuildings or integrated into the building. The following text looks at three alternatives to the classic photovoltaic roof.

 

Solar system on the garage roof

The garage roof is well suited for a photovoltaic system. This is often large enough to accommodate at least three kWp. Garages are usually designed as a flat roofs so that the PV modules are elevated.

 

To avoid damage to the roof skin, fastening systems without roof penetration are usually used here. This requires additional ballast, usually in the form of weighing stones.

 

Use a carport to generate electricity.

Carports can be set up quite easily and inexpensively. The special form of the solar carport is particularly worthwhile due to the dual function of parking lot roofing and energy generation.

 

Existing carports often cannot bear the additional weight of modules, so a solar carport should be planned before construction begins.

 

The solar modules of a PV carport are usually integrated directly into the roof. Partially transparent solar panels are often used for a special look, letting some sunlight through. Solar carports can achieve 3 to 10 percent more profit through bifacial photovoltaic modules through the functional rear.

A solar façade can be used if all roof areas are already occupied or unsuitable for photovoltaics.

 

Façade photovoltaics are either integrated directly into the building or retrofitted. In-house integration is up to 200 percent more expensive than retrofitting.

 

The modules are seamlessly integrated into the house and are less conspicuous.

 

Normally, the modules in a facade system are simply screwed flat to the outer wall; one also speaks of vertical photovoltaics. But there is also the option of choosing a small angle of attack.

 

Flat modules achieve a 30 percent lower annual yield than roof systems due to the unfavorable angle of incidence of the sun’s rays. PV facades are particularly useful on the south side. On differently oriented walls, the power generation is even worse.