What is a rooftop solar power system?

Turn unused roof space into electricity—even when structural considerations preclude a traditional system. Logic Energy designs, builds, and operates commercial rooftop PV systems—including above-roof, in-roof, and flat-roof systems—and, with its proprietary roof bridging system, can even make use of buildings that other providers would reject.

~70 %
Market Share: Rooftop
Ages 7–12
Typical Payback Period
up to 90%
Self-consumption During Daytime Operations
up to 5 MWp
On industrial flat roofs

Why Choose Logic Energy for Your Rooftop Solar System?

In short: Logic Energy has been planning, building, and operating commercial rooftop solar systems in Germany for over a decade—from feasibility studies to structural analysis and grid connection to ongoing monitoring, all from a single source. The company’s proprietary rooftop bridging system also makes it possible to install systems on buildings whose structural design would normally preclude the use of a traditional roof load.

Everything under one roof

Feasibility, structural analysis, planning, construction, and operation—a single point of contact from site selection to monitoring.

Proprietary Roof Bridging System

Makes buildings with low load-bearing capacity suitable for solar panels—roofs that others reject become usable.

Personal liability of the owner

The contracting party for investments is mediplan Helm e.K., which is personally liable under Sections 1, 17, and 19 of the German Commercial Code (HGB).

High self-consumption rate

Use up to 90% of solar power directly on-site—for facilities with high daily energy needs, this significantly reduces electricity costs.

The Three Installation Methods: Above-Roof, In-Roof, and Flat Roof

In short: A rooftop PV system consists of solar modules, a mounting structure, and inverters that are installed on or within a building’s roof. Three installation methods dominate the German market: rooftop photovoltaics (panels mounted above the roofing, with a market share of about 70%), in-roof photovoltaics (panels replace the roofing), and flat-roof mounting systems on commercial and industrial buildings.

The components are the same for all three types of installations: solar modules with solar cells, a mounting structure, the inverter—which converts the generated direct current into grid-compatible alternating current—as well as meters and cabling. Monocrystalline panels are most commonly used as PV modules; robust glass-glass modules are widely used on commercial roofs with a long service life. A commercial rooftop PV system thus differs clearly from a balcony power plant or small mini-solar systems for residential use—these are permanently installed systems with high photovoltaic output.

Photovoltaics convert sunlight directly into electricity and do not produce any greenhouse gases or pollutants during operation. The service life of a rooftop system is typically over 20 years—panels usually come with performance warranties of 25 to 30 years, and the inverter is typically replaced once during the system’s lifecycle. Ongoing operating costs are low and are essentially limited to insurance, monitoring, and occasional maintenance.

Roof-mounted is the most common installation method: The modules are placed on top of the existing roof covering, which remains the water-bearing layer; on a tile roof, roof hooks secured beneath the tiles hold the modules in place. In-roof systems integrate the modules into the roof surface and replace the roof covering—they offer a high-quality appearance but are more expensive and are generally better suited for new construction or roof renovations. Flat-roof systems are mounted on supports, facing south or in an east-west orientation for a more consistent daily power output curve.

A Comparison of the Three Installation Methods for Rooftop PV Systems
Construction MethodTypical system sizeAnnual Yield (Central Germany, South)Typical application
Roof-mounted (sloped roof) 5 kWp – 1 MWp 950–1,050 kWh/kWp Gable roofs, commercial buildings with a slope
Integrated into the roof 5–50 kWp 900–1,000 kWh/kWp New Construction, Roof Renovation, Prestige Projects
Flat roof (elevated) 100 kWp – 5 MWp 900–1,000 kWh/kWp (south), 830–920 kWh/kWp (east-west) Industrial and Logistics Buildings
Source: BSW-Solar, Market Statistics 2025; Fraunhofer ISE LCOE Study, July 2024. Figures are approximate and vary depending on location and design.

Is your roof suitable for a solar power system?

In short: A roof is suitable for a PV system if its structural integrity, orientation, and remaining service life are adequate. The key factor is the load-bearing capacity: 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 generally suitable; north-facing and heavily shaded areas are usually unsuitable.

Structural Engineering: The key question is point load versus distributed load. Older industrial buildings often have structural reserves covering only 30–60% of the roof area because trapezoidal profiles between the trusses have limited load-bearing capacity. Only a structural analysis report can provide a definitive answer—rules of thumb are no substitute. If the structural reserve is insufficient, a roof bridging system is an alternative that transfers the load to the main trusses rather than to the roof sheathing.

Orientation and Tilt: The compass direction determines the specific yield. South at 30° is considered the reference (100%); east-west orientation yields slightly less, but the output is more consistent throughout the day. Roof Condition: The roof’s remaining service life should cover the system’s operational lifespan—renovating the roof after installation is expensive.

System Size: The appropriate system capacity depends on the roof area and the business’s electricity demand. As a rule of thumb, a rooftop PV system requires about five to seven square meters of module area per kWp; modern monocrystalline modules will achieve an efficiency of about 20 to 23 percent by 2026 (Fraunhofer ISE, as of May 2026). A 10 kWp system therefore occupies roughly 45 to 55 m². For commercial roofs, the photovoltaic capacity scales according to the available area.

Yield by Orientation and Tilt (Reference: South 30° = 100%)
OrientationInclinationRelative ReturnSpecific annual yield
South30°100 %≈ 1,000 kWh/kWp
South10° (flat roof)95 %≈ 950 kWh/kWp
East-West10° (flat roof)92 %≈ 920 kWh/kWp
East or West30°85–90%850–900 kWh/kWp
North30°70 %≈ 700 kWh/kWp
Source: Fraunhofer ISE, July 2024. Values for Central Germany; regional solar irradiance and shading affect the results.

The Roof Bridging System: Useful Where Others Say No

In short: The roof bridging system is a substructure used by Logic Energy that transfers the module load not to the roof sheathing, but to the load-bearing trusses and exterior walls of a building. This eliminates deflection and localized loads on trapezoidal profiles. Typical application: 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 uplift, not the full PV load. This makes it possible to use buildings that were previously structurally unsuitable for a conventional load—roofs that other providers reject can thus be utilized.

Which buildings benefit the most?

In short: Roof-mounted systems are most cost-effective on buildings with high daytime electricity consumption and large roof areas. Manufacturing and logistics facilities with continuous daytime operations achieve self-consumption rates of between 70 and 90 percent. Standard commercial buildings without continuous production tend to achieve rates of 30–50 percent without storage—in such cases, the economic viability shifts toward feeding electricity into the grid.

Production and industrial facilities operating on a single or multi-shift basis can cover nearly all of their solar power needs themselves—the base load is generated during daylight hours. Logistics and warehouse facilities offer very large, often unused flat roofs; self-consumption depends on the operation of the cooling, conveyor, and loading infrastructure. Office buildings and retail facilities have significant daytime demand but smaller roofs. Agricultural buildings—barns, machinery sheds, and storage facilities—combine large roof areas with energy consumption that can be well managed through storage or revenue sharing.

Potential for Self-Consumption by Building Type (without Storage)
Building TypeRoof areaSelf-consumption rate (per day)Distinctive feature
Production/Industrial Buildinglarge70–90%Continuous base load during daytime operations
Logistics/Warehousevery large40–80%Depending on the cooling and charging infrastructure
Office Buildings / Retailmedium30–60%High daily requirements, smaller area
Agricultural Buildinglarge30–70%Good for storage or profit sharing
Source: SMA Solar, Commercial Self-Consumption Reference Guide, 2024. Values depend on the load profile and are provided for guidance only.

Solar Mandate: What Applies in Your State

In short: As of early 2026, ten federal states have introduced a solar mandate for non-residential buildings that requires rooftop solar systems for new construction or major roof renovations. Typical coverage rates range from 30–60% of the suitable roof area. Details vary by state law; North Rhine-Westphalia (NRW) plans to expand the renovation mandate starting in 2026.

The specific occupancy rate and the triggering event—new construction, renovation, or roof renovation—vary from state to state. The following overview lists the rate and legal basis for each state as of Q1 2026. The current statutory text of the respective state always takes precedence.

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. In addition, since 2023, a 0% value-added tax rate has applied to the purchase and installation of a PV system (Section 12(3) of the Value-Added Tax Act (UStG)), and systems up to 30 kWp per unit are exempt from income tax (Section 3 No. 72 of the Income Tax Act (EStG))—for smaller roofs, this reduces electricity costs and saves money without any bureaucratic hassle. The article on “Photovoltaics, Taxes, and Savings” discusses in detail how these incentives and other factors affect cost-effectiveness.

Solar Mandate for Non-Residential Buildings in Germany (Overview, as of Q1 2026)
StateOccupancy rateLegal basis
Baden-Württemberg60% of the suitable areaClimate Act of Baden-Württemberg, Section 8a
Berlin30% of the gross roof areaBerlin Solar Energy Act, Section 3
Hamburg30% of the suitable areaHmbKliSchG § 16
Hessein accordance with state regulationsHEG § 9
Lower Saxony50% of the suitable areaSection 32a of the Climate Act
North Rhine-Westphaliain accordance with state guidelines (expanded starting in 2026)NRW Building Code § 42a
Rhineland-Palatinate60% of the suitable areaLSolarG RP § 3
Schleswig-Holsteinin accordance with state regulationsEWKG § 9
Bremen50% of the suitable areaBremSolarG § 2
Source: respective state laws, as of Q1 2026. As of Q1 2026, Brandenburg, Mecklenburg-Western Pomerania, Saxony, Saxony-Anhalt, Thuringia, and Saarland do not have a general solar installation requirement for existing commercial buildings; regulations for new construction exist in some cases. Information provided without warranty—the current text of the law is authoritative.

5 Steps to a Complete Roof System

In short: A commercial rooftop solar system goes through five phases at Logic Energy: feasibility study with a roof inspection, structural analysis, and grid connection assessment; 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.
1

Roof Analysis

Check roof structure, load-bearing capacity, and grid connection · 2–4 weeks

2

Detailed Planning

Design, construction method, and, if applicable, bypass system

3

Approval

Grid Connection Commitment and Approvals

4

Construction

Installation and Commissioning

5

Monitoring

Day-to-Day Operations and Profit Monitoring

Done

Total completion time: 4–9 months, depending on size

The first step is a feasibility study: the roof structure, load-bearing capacity, and grid connection capacity are assessed before a cost estimate can be provided. If the structural analysis indicates insufficient load-bearing capacity, Logic Energy evaluates a roof bridging system as an alternative to roof renovation. This is followed by detailed planning, obtaining approval with a grid connection commitment, construction and commissioning, as well as ongoing monitoring of the system.

The following applies to connection to the power grid: Every photovoltaic system must be reported to the local grid operator and registered within one month in the Federal Network Agency’s market master data registry—without this registration, there is no entitlement to EEG remuneration. The solar power generated can be used on-site or fed into the public grid. For electricity fed into the grid, grid operators and energy suppliers pay a statutory feed-in tariff; for new systems up to 10 kWp, this has been 7.70 cents per kWh (partial feed-in) since August 2026 and is valid for 20 years from the date of commissioning (Federal Network Agency, as of Feb 2026). Logic Energy handles the registration and grid connection for the project.

The guide *Photovoltaics for Industry & Commerce* provides a detailed breakdown of costs, including funding options and a profitability analysis.

System Costs for Turnkey Roof-Mounted Solar Power Systems by System Size (2026)
Equipment segmentTurnkey €/kWpSource
5–10 kWp€900–€1,500 per kWpFraunhofer ISE / BSW-Solar, Q1 2026
30–100 kWp€800–€1,300 per kWpFraunhofer ISE / BSW-Solar, Q1 2026
100–500 kWp€700–1,100 per kWpFraunhofer ISE / BSW-Solar, Q1 2026
500 kWp and up€600–1,000 per kWpFraunhofer ISE / BSW-Solar, Q1 2026
Source: Fraunhofer ISE / BSW-Solar Price Monitor Q1 2026. The benchmark average for turnkey systems is approximately 1,015 €/kWp (Fraunhofer ISE, July 2024). These figures are for reference only; actual calculations depend on the roof structure, structural analysis, and grid connection.

Is your roof a good fit? Let's find out.

We'll assess the load-bearing capacity, orientation, and utility connection, and let you know whether a traditional rooftop solution or the roof bridging system is right for your building—with no obligation.

Request a Free Roof InspectionCost-Effectiveness in Detail

Battery Storage: When It's Worth It

In short: A battery storage system shifts excess solar power from the daytime into the evening hours and increases the self-sufficiency rate—which typically ranges from 30–50% without storage—to up to 70% when the system is sized to meet demand (HTW Berlin, Electricity Storage Inspection 2024). In contrast, a storage system is hardly cost-effective when power is generated only during the day and there is a high base load.

The economic sizing depends on the load profile. For single-shift production, direct self-consumption is already 70–90% even without storage—a solar power storage system offers little additional benefit in this case. It becomes worthwhile when load peaks occur outside of daylight hours, when charging stations for electric vehicles are used in the evening, or when the goal is to increase self-sufficiency. A storage system is sized based on usable capacity—starting at around 10 kWh for smaller commercial installations, and correspondingly higher for larger solar systems. The technical basics are explained in the “PV Battery Storage” technology pillar.

A Rooftop Solar System as an Investment—Without Owning Your Own Property

In short: In addition to personal use, a rooftop system can also be structured as an investment—either as a direct purchase of a system or as a profit-sharing arrangement in pre-planned systems, without owning a property. The page “Become a PV Investor” explains how this works; “Solar Power Without Equity” explains how to get started without equity. Return figures are historical and do not constitute a guarantee.

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.

Is the IAB worth it for photovoltaic systems?

The IAB is worthwhile for active businesses, freelancers, and investors with taxable profits below the 200,000-euro threshold, a high marginal tax rate, and a commercial solar system exceeding 30 kWp, at least 90% of whose electricity is used for business purposes. It is not worthwhile for tax-exempt systems up to 30 kWp (Section 3, No. 72 of the Income Tax Act) or for systems without an active business.

Whether the investment deduction is worthwhile is not a matter of the size of the investment alone, but of the tax environment. Four factors are decisive: Is there a taxable profit from which the deduction can be taken? Is this profit less than 200,000 euros in the year of the deduction? What is the individual marginal tax rate—since the tax relief is proportional to it? And is the investment realistically scheduled to take place within the three-year period? Anyone who can answer “yes” to all four questions has, with the IAB, one of the most powerful tax tools available under German law at their disposal.

Who Benefits from the IAB — and Who Doesn't

IAB MAKES SENSE The IAB is worth it
  • Active business with profit-based income —sole proprietors, partnerships, corporations, self-employed professionals, farmers, and foresters
  • Investor with a direct investment in a commercial PV system, properly classified as a separate movable asset
  • Profit in the tax year of less than €200,000
  • System with a capacity of over 30 kWp; ≥ 90% of the electricity is used for operational purposes
  • High personal marginal tax rate (proportional effect)
  • Investment Realistically Planned Within 3 Years
IAB BLOCKED / POINTLESS The IAB isn't worth it
  • Residential solar power systems up to 30 kWp – Section 3, No. 72 of the Income Tax Act (EStG) applies; no deductible profit arises
  • More than 10% of the property is used for personal residential purposes
  • No category of income —pure asset management or capital investor without a business
  • Profit of over €200,000 in the tax year
  • IAB: purely speculative , "for future use," with no intention to invest

The dividing line is not between large and small, but between taxable and tax-exempt. A farmer with a 300-kWp greenhouse roof system, a logistics company with an open-field solar park, and a freelancer with a commercial direct investment are on one side. On the other side are residential PV systems up to 30 kWp, systems where the electricity is primarily consumed by the owner, and pure equity investments without a commercial component.

Calculation Example: IAB for a 100,000-Euro Investment

Calculation Example: The Net IAB Effect on a €100,000 Investment (as of July 2026)
Position Amount / Value
Planned Investment (Estimated Acquisition Costs) 100.000 €
IAB Advance Deduction (50%, Section 7g(1) of the Income Tax Act) – in the year of deduction, prior to the purchase − 50.000 €
Assumed marginal tax rate 42 %
Tax Deferral in the Year of Deduction (Pure IAB) ≈ 21.000 €
Conceptual example, pure IAB effect. When combined with special depreciation (§ 7g, para. 5) and declining-balance depreciation, the cumulative tax relief over two fiscal years rises to up to 77.5%—27.5% in the investment year alone. That amounts to €77,500 in expenses → approximately €32,550 in tax benefits at a 42% tax rate. The detailed calculation is explained in the main tax article. The marginal tax rate is an assumption; your individual rate may vary. This is not tax advice. Source: Section 7g of the German Income Tax Act (EStG).

This example illustrates the pure IAB effect: A planned investment of 100,000 euros results in an upfront deduction of 50,000 euros, which reduces taxable income in the year of the deduction—before the purchase is made. Assuming a marginal tax rate of 42 percent, this corresponds to a tax deferral of approximately 21,000 euros. Combined with the special depreciation under Section 7g(5) of the German Income Tax Act (EStG) and declining-balance depreciation, the cumulative tax relief over two fiscal years rises to up to 77.5 percent of the investment amount—that is, 77,500 euros in expenses and thus a tax benefit of 32,550 euros at a 42 percent tax rate. In the year of investment itself, the relief is 27.5 percent, because the 50 percent IAB is already incurred in the year prior to the purchase. This figure assumes a purchase in January; if the asset is put into service in October, the relief drops to approximately 71.9 percent. You can find the detailed calculation of how these mechanisms combine in our main tax article. The marginal tax rate is an assumption; your individual rate and the specific impact depend on your overall situation.

When the IAB Does Not Apply: The Exclusion Under § 3 No. 72 of the Income Tax Act (EStG)

For systems up to 30 kWp per residential or commercial unit, the tax exemption under Section 3, No. 72 of the Income Tax Act (EStG) applies. These systems do not generate taxable income—and thus no profit from which an IAB could be deducted. For the typical residential or small-scale system, the IAB is therefore not a useful tool, regardless of the individual’s tax rate. It only takes effect above the 30-kWp threshold, on a commercial scale. Details on this special situation are provided above in the section on the special legal situation.

Risks: What Could Bring Down the IAB

The Four Risks Identified by the IAB—and How Significant They Are
Risk What happens Weight
No purchases within 3 years Retroactive reversal in the year of deduction, back taxes + interest at 1.8% per annum (Section 233a in conjunction with Section 238 of the German Fiscal Code (AO)) High
Profit threshold of €200,000 exceeded IAB is not permitted in the year of deduction—the advance deduction is eliminated entirely Medium
90% utilization broken / no clear operational basis Recognition does not apply; the IAB is reversed (e.g., in the case of high private consumption) Medium
Unresolved BFH Case Law Regarding Tax-Exempt Investments Under the Old IAB Legal Uncertainty Regarding Existing Cases of ≤30 kWp (Case III R 39/25, pending as of July 2026) Observe
The Logic Energy editorial team’s traffic light classification is provided for informational purposes only and does not constitute tax advice. Legal basis: Section 7g, paras. 1–4 of the Income Tax Act (EStG), Sections 233a and 238 of the Tax Code (AO), Federal Fiscal Court (BFH) III R 39/25.

The IAB is an advance payment from the tax office for an investment that has not yet been made—and that is precisely where its risks lie. If the planned investment is not made within three years, the tax office retroactively revokes the deduction in the original year and charges interest on the additional tax liability at the current rate of 1.8 percent per year. If business use falls below the 90 percent threshold or if profits exceed the 200,000-euro limit, the deduction is forfeited. That is why the rule of thumb is: only claim the IAB once the investment has been definitively decided—not speculatively in advance.

Should you check the IAB for your PV investment?

Logic Energy designs and builds systems precisely within the size range covered by the IAB in a legally compliant manner—commercial rooftop systems, ground-mounted solar parks, and agri-PV. Your tax advisor will handle the tax assessment on a case-by-case basis.

More About PV InvestmentsSchedule an initial consultation

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

What is a rooftop solar power system?

A rooftop PV system is a photovoltaic system that is installed on or within the roof surface of a building. Three installation methods are predominant: above-roof (modules installed over the roofing material, with a market share of about 70%), in-roof (modules replace the roofing material), and flat-roof (mounted on a support structure). For commercial applications, the roof type is the primary factor in determining the appropriate solution.

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

A roof is suitable if its structural integrity, orientation, and remaining service life are adequate. 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 not a problem; north-facing and heavily shaded areas are usually unsuitable. Only a structural engineering report is valid.

How much will a commercial rooftop solar system cost in 2026?

Turnkey rooftop systems ranging from 100 to 500 kWp will typically cost between 700 and 1,100 €/kWp in 2026, while smaller commercial systems (30–100 kWp) will cost between 800 and 1,300 €/kWp (Fraunhofer ISE / BSW-Solar Price Monitor, Q1 2026). The benchmark average for turnkey systems is approximately 1,015 €/kWp (Fraunhofer ISE, July 2024).

How does the roof bypass system work?

A galvanized steel support structure spans the roof and transfers module, snow, and wind loads to the main load-bearing trusses and exterior walls rather than to the roof sheathing. This makes it possible to use buildings with low load-bearing capacity that would otherwise be unsuitable for a traditional on-roof installation. An air gap further improves rear ventilation.

What is the payback period for a commercial rooftop solar system?

Typically 7–12 years; 5–8 years if there is a high level of self-consumption during daytime operations. The exact figure depends on the price of electricity, the size of the system, its orientation, and the proportion of self-consumption. The economic details are provided in the “Photovoltaics for Industry and Commerce” guide. All information is provided without guarantee.

Does a commercial rooftop solar system always need a battery storage system?

No. In pure daytime operation with a high base load, direct self-consumption is already 70–90% even without storage; in that case, storage is hardly worth the investment. It becomes worthwhile when there are peak loads outside of daylight hours. Storage increases the self-sufficiency rate from 30–50% to up to 70% (HTW Berlin, 2024).

Can I use a rooftop solar system as an investment?

Yes. In addition to personal use, a rooftop system can be utilized through a direct purchase or as a profit-sharing arrangement, even if you don’t own your own property. The “Become a PV Investor” page explains the terms, structure, and process. Return figures are historical and not guaranteed.

Turn your roof into a source of energy.

Whether it’s a traditional rooftop solution, a flat-roof mounting system, or a roof-bridging system for structurally challenging situations—we’ll find the right design for your building and support you every step of the way, from analysis to operation.

Request a Free Roof InspectionInvest

References

Related Pages: A Custom PV System for Your Business · Ground-Mounted Photovoltaics · Agri-Photovoltaics · PV as an Investment