What is a rooftop solar power system?

And which type of roof is best suited for which business?

A rooftop PV system is a photovoltaic system that is installed directly on or within the roof surface of a building—as a rooftop, in-roof, or flat-roof system. For commercial buildings, the roof type is the primary determining factor: gable roofs allow for rooftop solutions starting at around 5 kWp, while flat roofs on industrial buildings typically support 150 kWp up to several MWp (Fraunhofer ISE, LCOE study, July 2024).

Table of Contents

  1. What Is a Rooftop Solar System? – Definition and Three Basic Types

  2. What type of roof is suitable for a solar power system?

  3. How does the Logic Energy roof bypass system work?

  4. Which types of buildings benefit most from a rooftop solar system?

  5. Solar Mandate: What are the requirements in your state?

  6. How does Logic Energy plan and build a rooftop solar system?

  7. What role do battery storage systems play in a rooftop solar system?

  8. A rooftop solar system as an investment—when is that possible?

  9. FAQ

  10. Sources

A technician working on a solar roof, with the city in the background, in black and white.

Any business owner or farmer planning a rooftop PV system faces three fundamental technical decisions before a single cost estimate makes sense: Which system type is suitable for the existing roof—rooftop, in-roof, or flat roof? Can the roof structure support the additional load? And can the roof still be used if the load-bearing capacity is insufficient? This Pillar answers the technical questions regarding rooftop photovoltaics. It serves as the technical guide to rooftop systems—not the purchasing process (for which there is the page on installing your own PV system for business use) and not the economic feasibility comparison (for which there is the complete guide Photovoltaics for Industry and Commerce 2026).

Logic Energy, a brand of mediplan Helm e.K. and part of the Helm Group, has been designing and installing commercial rooftop solar systems in Germany for over a decade—including on industrial buildings where structural considerations initially seem to preclude the use of conventional rooftop systems. The technical recommendations in this text are based on our own project experience as well as on primary sources such as Fraunhofer ISE, BDEW, and HTW Berlin.

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What Is a Rooftop Solar System? – Definition and Three Basic Types

A rooftop photovoltaic system consists of solar modules, a mounting structure, and inverters installed in or on a building’s roof. Three installation methods dominate the German market: rooftop photovoltaic systems (panels mounted above the roof covering, approximately 70% market share), in-roof photovoltaics (panels replace the roof covering), and flat-roof mounting systems (standard for industrial buildings).

The term "rooftop system" distinguishes rooftop photovoltaic systems from two other types of systems: ground-mounted systems onplots of land and agri-PV systems installed overagriculturalland. Technically, arooftop photovoltaic systemdiffersfrom both primarily due to the limited module area, wind load conditions, and dependence on the existing roof structure. Depending on the building type and roof covering, different modules, mounting systems, and installation methods may be considered.

Brief definition: A rooftop solar power system consists of solar panelsinstalled on a building’s roofto convertsunlight into electricity.This electricity can be used directly within the building,stored temporarilyin a battery,or fed into the public grid.

Roof-mounted solar panels – the most common installation method

In a roof-mounted installation, aluminum rails are attached to the rafters using roof hooks; the solar modules are clamped onto them. The roof covering—tiles, corrugated metal, or fiber cement—remains intact and watertight. Advantages: comparatively low cost per kWp, standardized installationwith shortsetup times, excellent rear ventilation, and easy replacement ofindividual modules. Disadvantages: visually visible in front of the roof surface; tiles beneath the roof hooks must be professionally fitted; each roof hook is a potentialentry point for moisture—whichmakes properinstallation essential.

In-roof photovoltaics– when the roof covering is being replaced

In an in-roof photovoltaic system, special in-roof solar modules replace traditional roofing materials—roof tiles, slate, or roof shingles are omitted where the modules are installed. The in-roof modules feature a water-carrying frame, thereby serving both as roofing and as a means of generating electricity. In-roof photovoltaics is the only construction method in which the roof covering and the PV system form a single structural unit.

For existing roofs, an in-roof PV system is rarely cost-effective because the tilesare already in place.In-roof integrationmakes economic sense in two scenarios: for new construction and when aroof renovation is alreadydue—in these cases, the costs for roof tilesor conventional roofingaresaved, and only the difference between in-roof modules and traditional roof tiles is incurred. A common approach: renovating the roof and installing an in-roof PV system in a single step, since scaffolding and labor costs are incurred only once.

Advantages of the in-roof system: a flush appearance (often a requirement for historic buildingsor under zoning regulations) and the elimination ofmaterial costs for the replaced roof covering. Disadvantages: reduced rear ventilation(a few percent lower yield in summer), higher installation costs per kWp, and a tighter integration with the roof surface—any future modifications will affect the entire roof structure. Compared to above-roof mounting, installation is more complex and takes longer per square meter.

It is important to distinguish between in-roof solar modules and solar roof tiles (also known as solar tiles): While in-roof photovoltaic modulesare full-surface module elements thatreplaceseveralsquare metersof roofing at once, solar roof tiles mimicthe shape of individual roof tiles and are installed tile by tile. A complete solar roof made of solar tiles remains a niche product in Germany, primarily in high-end residential construction; in the commercial sector, traditional in-roof PV systems dominate. Anyone looking for a photovoltaic solution for a residential roof or a small commercial building has three options:standard rooftop solar modules, in-roof solar modulesfor new constructionor renovation, and solar roof tiles as a premium aesthetic option with lower module output per square meter.

Typical applications for an in-roof photovoltaic system include new commercial buildings with high architectural standards, historic buildings, and projects that combine roof renovation with PV installation on older buildings. In-roof solar modules also serve as roofing material, so the total weight is often lower than that of roof tiles combined with rooftop solar modules. An in-roof PV system is therefore not merely an alternative to rooftop installation, but a distinct construction method with its own structural, drainage, and installation requirements.

In-roof photovoltaics remaina niche marketinGermany compared to rooftop modules, but they are wellestablished: Several manufacturers offer in-roof solar modules with certified test reports that integrate into standard tile sizes. Installing an in-roof PV system takes longer per square meter than a comparable rooftop installation—a difference that is reflected in the total cost.

Flat-roof mounting – East-West vs. South

On flat roofs—which are common on industrial buildings, logistics centers, and shopping malls—photovoltaic modules aremounted on ballast frames or lightweightmounting structures. Unlike with rooftop orin-roof systems,no penetration of the existing roof surface isrequired; ballast-based mounting speeds up installation and minimizes disruption to the roof covering. Two approaches compete: south-facing orientation with a 10–15° tilt (highest peak yield, but a sharp generation peak at midday) and east-west orientation with pairs of modules (about 8% lower annual yield per kWp ,but a flatter generation profile andabout 30% more installed system capacity per square meter). For businesses with high self-consumption throughout the day, an east-west orientation is often the more economical choice compared to a south-facing orientation.

Comparison of the three types of rooftop systems
Feature Roof-mounted Integrated into the roof Flat roof Source
Typical additional load per square meter 15–20 kg 20–25 kg (replaces bricks) 20–80 kg (depending on ballast) Manufacturer specifications: SL Rack, K2 Systems 2024
Typical power range 5 kWp – 1 MWp 5–50 kWp 100 kWp – 5 MWp BSW-Solar, Market Statistics 2025
Annual yield in Central Germany (south-facing) 950–1,050 kWh/kWp 900–1,000 kWh/kWp 900–1,000 kWh/kWp (south), 830–920 kWh/kWp (east-west) Fraunhofer ISE LCOE Study, July 2024
Best roof for this type Gable roof, shed roof, corrugated metal New construction, roof renovation Industrial building, logistics center, warehouse Logic Energy, Project Practice 2024
Are roof penetrations necessary? Yes (roof rack) Yes (built-in) No (ballast possible) Sub-structure Manufacturers 2024

What type of roof is suitable for a solar power system?

A roof is suitable for a PV system if its structural integrity, orientation, and remaining service life are adequate. The load-bearing capacity is crucial: Rooftop and flat-roof systems typically require an additional load of 15–25 kg per m². East-, south-, and west-facing roofs with a pitch of 10–45° are suitable; north-facing and heavily shaded areas are usually unsuitable. The roof must have a remaining service life of at least 20 years.

Structural Engineering: Point Loads vs. Area Loads and Typical Industrial Roof Problems

Structural load capacity is the most common deal-breaker for existing industrial buildings. Modern trapezoidal sheet metal or sandwich panel industrial roofs from the 1980s and 1990s were designed to withstand snow and wind loads—the additional, permanent PV load of 15–25 kg/m² was not factored in. Particularly critical are localized load concentrations on mounting systems: A ballast frame often concentrates the mass on individual trapezoidal high ribs, while the supporting structure is designed for distributed loads. A structural analysis clarifies before planning begins whether the roof covering and the underlying purlins can support the load. A common finding in older industrial buildings: The structural reserve is sufficient for 30–60% of the theoretical module area—not for full coverage.

Orientation, Tilt, and Shading

Annual yield depends on the combination of orientation (azimuth) and tilt. A south-facing orientation with a 30° tilt is considered the reference case (100% yield). East-west-facing installations on flat roofs achieve about 92%, purely east- or west-facing roofs around 85–90%, and flat north-facing slopes up to 70%. Shading—such as from neighboring buildings, chimneys, antennas, or trees—not only reduces the output of the shaded modules but can also cause entire rows of modules to be taken offline via string inverters. Power optimizers or MPP trackers in module inverters mitigate this issue but do not completely solve it.

Roof condition and remaining service life

A cost-effective PV system has a lifespan of 25–30 years. The roofing material underneath should have at least 20 years of remaining service life. Installing a photovoltaic system on a rotten tile roof or corroded corrugated metal will result in costly removal and reinstallation within a few years. If renovation is expected within ten years, it is recommended to either combine roof renovation with in-roof integration—or to commission the renovation work in advance.

Advantages and Disadvantages of a Rooftop Solar Array

The advantages of a rooftop PV system are obvious: existing roof space is put to dual use, the installation does not require any additional ground space, self-consumption at the point of generation saves on grid fees, and the system’s output can be tailored to the building’s load profile. In addition, there are tax benefits, and in ten federal states, it fulfills a legal obligation (see the “Solar Mandate” section). The disadvantages include dependence on the existing roof: structural integrity, orientation, and the roof’s age impose strict limitations. Those with a roof that has poor orientation or insufficient load-bearing capacity rarely find a cost-effective solution—in such cases, lease models or an off-site system are the better alternatives.

Yield of a rooftop solar array depending on orientation and tilt (Central Germany)
Orientation Inclination Relative yield (South 30° = 100%) Specific annual yield Source
South 30° 100 % ≈ 1,000 kWh/kWp Fraunhofer ISE, July 2024
South 10° (flat roof) 95 % ≈ 950 kWh/kWp Fraunhofer ISE, July 2024
East-West 10° (flat roof) 92 % ≈ 920 kWh/kWp SMA Solar, Commercial Self-Consumption
East or West 30° 85–90% 850–900 kWh/kWp Fraunhofer ISE, July 2024
North 30° 70 % ≈ 700 kWh/kWp Fraunhofer ISE, July 2024

How does the Logic Energy roof bypass system work?

The roof bridging system is a substructure used by Logic Energy that transfers the weight of the modules not to the roof deck, but to the load-bearing trusses and exterior walls of a building. This eliminates deflection and localized loads on trapezoidal profiles. Typical applications: industrial roofs with low load-bearing capacity, where a conventional on-roof solution would not be permitted.

For many older industrial buildings, a rooftop system is ruled out for structural reasons before its economic viability has even been assessed. The traditional solution—renovating the roof before installing the PV system—often costs more than the system itself and does not pay for itself through electricity revenue. The roof bridging system resolves this conflict structurally: Instead of transferring the loads into the roof deck, a support structure spans the entire roof and transfers the weight of the modules as well as snow and wind loads directly to the main trusses and exterior walls.

Structurally, it consists of a box-girder or truss system made of galvanized steel that runs parallel to the ridge across the roof. The modules are mounted on this secondary support structure, not on the existing roof. An air gap remains between the beams and the existing roof surface, which additionally improves rear ventilation of the modules—a side effect that increases the specific yield by a few percent.

The design advantage: The load-bearing capacity of the existing roof need only be sized to accommodate the dead load of the bridging system plus wind loads, not the full weight of the PV system. This makes it possible to utilize industrial buildings that were previously structurally unsuitable for a conventional roof-mounted PV system. A detailed technical overview with manufacturer data and project references will follow in the planned feature article on the topic; the fundamental system logic has been implemented multiple times in industrial buildings through Logic Energy’s project practice.

Which types of buildings benefit most from a rooftop solar system?

Roof-mounted systems are most cost-effective on buildings with high daytime electricity consumption and large roof areas. Production and logistics facilities with continuous daytime operations achieve self-consumption rates between 70 and 90% (SMA Solar, Commercial Self-Consumption); standard commercial buildings without continuous production tend to be around 30–50% without storage. Office buildings, food retail stores, and agricultural buildings are also among the top candidates.

Production and industrial buildings

Production and industrial facilities are the traditional primary market for solar systems installed on industrial buildings: large, mostly unshaded flat roofs, long operating hours during the day, and high base-load consumption. A 500-kWp system on a production hall often covers daily consumption entirely in the summer; the self-consumption share during continuous daytime operation ranges from 70–90% depending on the industry, whereas in standard commercial scenarios without shift or continuous operation, it tends to be around 30–50%. The higher the self-consumption, the shorter the payback period—however, this is not calculated in figures on the rooftop system itself, but rather in the Photovoltaics Guide for Industry and Commerce 2026.

Logistics and Warehouses

Logistics and warehouse facilities have even larger roof areas, but often lower self-consumption: order picking and forklift traffic do not generate a constant base-load electricity demand like a production line does. The key factor here is whether refrigeration systems or electric charging points for vehicle fleets increase self-consumption. In lease-roof scenarios without on-site electricity consumption, the solar power model without equity (PPA) is often a more viable option.

Office buildings and retail

Office buildings typically have moderate roof areas and reliable daytime usage. On-site consumption is significantly boosted by air conditioning and server infrastructure. The food retail sector is one of the most economically robust segments: refrigeration and freezing generate high base-load consumption year-round, which aligns well with the PV generation profile.

Agricultural buildings

Livestock barns, machinery sheds, and storage buildings on farms in Germany have significant amounts of unused roof space. It is important to note the distinction: A PV system installed on a barn roof remains a traditional rooftop system—the distinction from agri-PV refers to the dual use of space over cultivated farmland. Barn roofs, particularly those of dairy and swine barns, often have good south and east-west orientations and are used throughout the day year-round (barn climate, milking robots).

Solar Mandate: What are the requirements in your state?

As of early 2026, ten federal states have introduced a solar mandate for non-residential buildings, requiring rooftop solar systems for new construction or major roof renovations. Typical coverage rates range from 30% to 60% of the suitable roof area. Details vary by state law; North Rhine-Westphalia plans to implement an expanded renovation mandate starting in 2026, while Bavaria will do so starting in 2025.

Solar requirements in Germany are regulated at the state level—there is no uniform federal requirement for commercial rooftops. The following overview reflects the situation as of early 2026 and is not a substitute for legal advice; the relevant state building energy laws apply.

Solar Mandate for Non-Residential Buildings in Germany (Overview, as of Q1 2026)
State Required for new non-residential buildings Requirements for roof renovation Occupancy rate Legal basis
Baden-Württemberg Yes (since 2022) Yes (since 2023) 60% of the suitable area Climate Act of Baden-Württemberg, Section 8a
Bavaria Yes (since 2023) Yes (since 2025, expanded) Depending on usage BayKlimaG, Section 44a
Berlin Yes (since 2023) Yes (since 2023) 30% of the gross roof area Berlin Solar Energy Act, Section 3
Hamburg Yes (since 2023) Yes (starting in 2025) 30% of the suitable area HmbKliSchG § 16
Hesse Yes (public buildings) Limited defined by state law HEG § 9
Lower Saxony Yes (since 2023) No 50% of the suitable area Section 32a of the Climate Act
North Rhine-Westphalia Yes (phased in through 2026) Yes (starting in 2026, major renovation) defined by state law NRW Building Code § 42a
Rhineland-Palatinate Yes (new commercial buildings of 100 m² or more) No 60% of the suitable area LSolarG RP § 3
Schleswig-Holstein Yes (since 2023) Yes (since 2025) Depending on usage EWKG § 9
Bremen Yes (since 2025) Yes (since 2025) 50% of the suitable area BremSolarG § 2

As of Q1 2026, Brandenburg, Mecklenburg-Western Pomerania, Saxony, Saxony-Anhalt, Thuringia, and Saarland have not introduced a general solar mandate for existing commercial buildings; regulations for new construction exist in some cases. Tax incentives such as the investment deduction under Section 7g of the Income Tax Act (EStG) as amended by the Growth Opportunities Act of 2024 apply nationwide and are explained in detail in a separate article: IAB under Section 7g EStG and the special depreciation allowance.

How does Logic Energy plan and build a rooftop solar system?

At Logic Energy, a commercial rooftop solar system goes through five phases: feasibility study (roof inspection, structural analysis, grid connection), detailed planning, permitting and grid connection approval, construction and commissioning, and monitoring. The roof analysis and preliminary structural analysis typically take 2–4 weeks; the entire project takes between 4 and 9 months, depending on the size of the system.

Project planning begins with a roof analysis: surveying, structural assessment (based on existing documentation or conducted by a structural engineer on-site), shading analysis, and evaluation of current electricity consumption. Only on this basis can the system size be determined to match the consumption curve; the roof analysis also provides an initial estimate of the cost per kWp.

Detailed planning includes the electrical design (strings, inverters, grid connection point), mechanical installation planning (including ballasting or—for challenging roofs—a roof bridging system), and applications to grid operators and building authorities. During the construction phase, the substructure and modules are installed; typical installation times for commercial PV systems range from a few days to several weeks. The main process from the contractor’s perspective is described separately on the page regarding operating your own PV system. Alternatively, Logic Energy offers the “Solar Power Without Equity” model, in which the system is financed by an investor and the electricity is procured through a long-term supply contract.

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Do you want to know if your roof is structurally sound, what type of system is suitable, and what size system would be appropriate? Logic Energy evaluates the structural integrity, orientation, and grid connection, and provides a detailed yield forecast.

→ Request a roof inspection (no obligation, free of charge)

What role do battery storage systems play in a rooftop solar system?

A battery storage system transfers excess solar power from daytime to evening hours and increases the self-sufficiency rate from a typical 30–50% without storage to up to 70% when sized to meet demand (HTW Berlin, Electricity Storage Inspection 2024). Cost-effective sizing depends on the load profile—with production limited to daytime hours, storage is rarely necessary.

A rooftop system generates electricity when the sun is shining. If the system operates continuously throughout the day, nearly all of the solar power goes directly to the equipment—in this case, a storage system offers little additional benefit. However, if daily consumption varies with the sun’s position or if there are peak loads in the early morning and late evening hours (typical for retail, office buildings, and agriculture with night milking), a storage system significantly improves the share of self-consumption.

Proper sizing is more of an art than a rule of thumb: if the system is too small, the battery will rarely be fully charged; if it is too large, the additional investment will not pay off over the system’s lifetime. This topic is covered in detail in the technical section on PV battery storage and, for commercial applications, in the article on the co-location of storage systems and rooftop installations.

A rooftop solar system as an investment—when is that possible?

In addition to owner-occupied use, rooftop systems can be structured as capital investments—either through the direct purchase of a system (“ready-to-build” projects) or through inverter-based revenue-sharing arrangements. Logic Energy structures such investments for investors starting at €100,000, with a market return of 6–10% per annum. (Helm Group, portfolio data 2024) and a base term of 20 years with an extension option up to 40 years. With IAB and special depreciation (AfA) incentives, pre-tax liquidity improves further in the first two years.

Not every rooftop system is financed by the building owner—many industrial and logistics rooftops are technically ideal, even if the facility owner does not wish to tie up capital. This is where two models diverge: In the lease model, the owner leases the roof space, an operator builds and operates the system, and supplies the electricity back via a PPA (see Solar Power Without Equity). In the investor model, an investor provides equity capital, while Logic Energy handles planning, construction, and operation.

For investors, rooftop systems represent a distinct asset class: approval processes are faster than for ground-mounted systems, individual units are smaller, and electricity prices are higher for self-consumers; however, they are dependent on the condition of the property and the creditworthiness of the roof owner. The investment model involving a share of inverter revenue is described in detail; a comprehensive overview can be found in *Photovoltaic Investment 2026*.

Estimated investment costs for 2026 (turnkey):

Turnkey System Prices for Residential PV Systems in 2026 (by System Segment)
Equipment segment Turnkey €/kWp Typical system size Source
Solar System for a Single-Family Home €900–€1,500 per kWp 5–10 kWp Fraunhofer ISE / BSW Solar Price Monitor Q1 2026
Commercial Rooftop Solar System €800–€1,300 per kWp 30–100 kWp Fraunhofer ISE / BSW Solar Price Monitor Q1 2026
Industrial Photovoltaic System €700–1,100 per kWp 100–500 kWp Fraunhofer ISE / BSW Solar Price Monitor Q1 2026
large-scale facility €600–1,000 per kWp 500 kWp and up Fraunhofer ISE / BSW Solar Price Monitor Q1 2026

The benchmark average cost of turnkey PV systems is approximately €1,015/kWp (Fraunhofer ISE, July 2024). A detailed cost breakdown, including incentive schemes (IAB under Section 7g of the German Income Tax Act, KfW 270, special depreciation), is provided in the 2026 PV Investment Guide.

Return Note: Return figures of 6–10% per annum are based on historical portfolio data from mediplan Helm e.K. / the Helm Group and do not constitute a guarantee of future returns. Photovoltaic investments are business investments that carry the risk of total loss. The relevant contract and sales documents are authoritative. Detailed risk disclosures can be found on the Risk Disclosure page.

From a technical standpoint, installing a rooftop PV system is not a question of “whether” but of “which type on which roof.” Rooftop systems are most common on gable roofs, while flat-roof mounting systems dominate the industrial sector, and in-roof systems fill useful niches in new construction and renovation projects. The key factor for cost-effectiveness is not primarily the module price, but rather the roof’s suitability—structural integrity, orientation, and remaining service life. If the load-bearing capacity of an existing roof is insufficient, the roof bridging system makes projects possible that would traditionally have failed. The service page describes the purchasing process for business owners looking to install their own PV system for their operations; detailed information on costs and incentives can be found in the PV Investment Guide 2026.

Request a roof inspection

Logic Energy will assess the structural integrity, orientation, grid connection, and projected energy output of your roof at no cost—whether it’s a rooftop, in-roof, or flat roof system.

→ Request a roof inspection (no-obligation, free of charge)

This article is intended solely to provide general information about rooftop solar systems and does not constitute investment, tax, or legal advice. Information regarding returns, costs, and project durations is based on market data and Logic Energy project calculations and does not guarantee future results. Statements regarding structural analysis, permits, and grid connection require an individual assessment on a case-by-case basis. Tax instruments such as the IAB under Section 7g of the German Income Tax Act (EStG) are subject to specific requirements. For your specific situation, please consult a licensed professional, financial, or tax advisor. All information is provided without warranty. As of: April 23, 2026.

For businesses:

YOUR ROOF. YOUR ENERGY FUTURE. YOUR RETURN ON INVESTMENT.

Do you have a commercial, industrial, or logistics building with unused roof space? Turn it into a profitable source of energy. With commercial solar systems, you can reduce electricity costs by up to 80%, increase your energy independence, and enhance your company’s image—all without any maintenance on your part.

What you get:

  • Drastic cost reduction

  • 70–90% self-consumption even without storage (during daytime operation)

  • With storage, self-sufficiency of over 80% is possible

  • Protection against rising energy costs

  • Making solar installation requirements profitable rather than merely compliant with the law

  • Increase property value

  • Improved ESG Reporting

Full-service support:
We handle planning, construction, maintenance, insurance, and operations (O&M)—you don’t have to lift a finger

Even for "challenging" roofs:
Many industrial roofs are considered "unsuitable for PV" because they can only support the weight in certain areas. With our proprietary roof bridging system, we make even these roofs usable—we can develop areas that other providers turn down.

You have two options:

Let’s work together to see if a solar power system is a good investment for your business—free of charge and with no obligation.

FOR INVESTORS:

ROOF-TOP SYSTEMS AS AN INVESTMENT – WITHOUT OWNING REAL ESTATE

Are you interested in investing in solar power—without owning commercial real estate yourself? With our rooftop solar investment model, you can invest in professionally developed solar projects on commercial, industrial, and logistics rooftops. We handle securing the rooftops, lease agreements, and all operational aspects—you invest in fully planned and approved systems.

What you get:

  • Ready-to-build roof projects (already planned and approved)

  • Investments in inverters starting at €100,000 or entire systems

  • 20–40-year term with predictable revenue from electricity sales

  • Secure lease agreements with building owners (20+ year term)

  • Personal liability of the owner (e.K.) – Agreement with our partners mediplan Helm e.K.

  • Financing assistance is available through our bank (typically 20–30% equity)

  • Full-service operations and maintenance (O&M): maintenance, insurance, monitoring, repairs

Why rooftop systems are particularly attractive as an investment:

  • Concrete savings for the building owner: The tenant/owner directly saves on electricity costs, which makes long-term contracts very stable

  • Compliance with solar installation requirements: Many states already require solar installations on commercial buildings—this creates demand and provides legal certainty for planning

  • Greater revenue security: Commercial facilities operating during daylight hours have a high level of self-consumption (70–90%), which means they are less dependent on fluctuating feed-in tariffs

  • Very stable lease agreements: Building owners remain at the location for the long term (unlike, for example, with open-space properties)

  • Tax-efficient: Many investors take advantage of the IAB (Section 7g of the German Income Tax Act) or special depreciation allowances (talk to your tax advisor about your specific options)

Two investment options:

  • Option 1: Inverter Investment (starting at €100,000)
    You purchase one or more inverters and receive the revenue generated by these inverters over a period of 20–40 years. Minimum investment: €100,000. Learn more in our guide on how to become a PV investor!

  • Option 2: Purchase the entire system (starting at approx. €500,000)
    You will acquire a complete rooftop system with all rights and obligations. Higher returns, full control, tax-optimized.

Minimum investment: €100,000 (inverter investment)

💡 Important Note: mediplan Helm e.K. and Logic Energy are not tax advisors or financial advisors. Many of our investors take advantage of tax planning options such as the investment deduction (IAB) under Section 7g of the German Income Tax Act (EStG). Please consult your tax advisor regarding the specific options available to you in your particular situation. This content is provided for general informational purposes only and does not constitute investment, tax, or legal advice. Return figures are based on historical data from the Helm Group and are not a guarantee of future results. For your specific situation, please consult a licensed financial or tax advisor. All information is provided without warranty. As of April 2026.

Engineers on a roof covered with solar panels; one is talking on a tablet while the others work, with the city skyline visible in the background.

FAQ

  • Typically 7–12 years; 5–8 years if there is high self-consumption during daytime operations. The exact figure depends on electricity prices, system size, orientation, and the proportion of self-consumption. The economic details are provided in the 2026 Guide to Photovoltaics for Industry and Commerce.

  • Only a structural engineering report can provide a definitive answer. Older buildings often have structural reserves covering only 30–60% of the roof area. If the reserve is insufficient, a roof bridging system is an alternative that transfers the load to the main trusses rather than the roof sheathing.

  • In most German states, rooftop solar systems installed on existing commercial roofs do not require a permit, provided that the building’s structure is not significantly altered. Exceptions include buildings subject to historic preservation, certain landscape conservation areas, and structural modifications that compromise the building’s stability. The utility company must approve the connection in all cases.

  • Solar modules typically come with performance warranties of 25–30 years, while inverters are usually replaced once during their lifecycle (lifespan of 10–15 years). If properly designed, the mounting structure made of galvanized steel or aluminum will outlast the modules without needing to be replaced.

  • Turnkey industrial rooftop systems (100–500 kWp) will typically cost €700–1,100/kWp in 2026, while smaller commercial rooftop systems (30–100 kWp) will cost €800–1,300/kWp (Fraunhofer ISE / BSW Solar Price Monitor Q1 2026). A detailed breakdown, including incentive mechanisms and a profitability analysis, is provided in the 2026 PV Investment Guide.

  • No. In purely daytime operation with a high base load (traditional single-shift production), direct self-consumption is already 70–90% even without storage; in such cases, storage is hardly cost-effective. It makes sense for peak loads outside of daylight hours—see the “PV Battery Storage” technical section for details.

  • Generally speaking, yes, provided that the roof area, grid connection capacity, and inverter capacity allow for expansion. The technical details regarding expansions will be covered in a separate article; future expansion should already be taken into account during the initial planning phase.

References