Taking over a PV system after roof lease:
What the 1-euro clause really means

At the end of a 25-year roof lease contract many building owners face an attractive option: taking over the PV system for a symbolic €1. What looks like a gift on paper requires a careful condition assessment in practice — because not every 25-year-old system is worthwhile.

What is behind the 1-euro clause?

In a roof lease for photovoltaics a building owner makes their roof surface available to an investor in return for remuneration — who in turn erects, operates and bears all risks of a PV system. At the end of the agreed term, usually 25 years, what happens to the system is regulated contractually.

Specialised providers who lease roof surfaces for photovoltaics, standardly grant the lessor the right to take over the fully paid-off system for €1. Ownership of modules, inverters, mounting structure and cabling passes to the building owner — including the ongoing income from grid feed-in or self-consumption.

Alternatively the investor can dismantle the system at their own expense and restore the roof to its original condition. This dismantling obligation is usually also laid down in the contract and secured by a limited personal easement in the land register.

What is a 25-year-old PV system still worth?

The good news: modern crystalline silicon modules are long-lasting. Manufacturers typically guarantee at least 80% of rated power after 25 years. In practice the degradation of high-quality modules is about 0.4–0.5% per year — meaning 87–90% of the original power is still present after 25 years.

The bad news: it depends heavily on the operating condition. A poorly maintained system can have lost 30–40% of its power after 25 years. And some components simply have a shorter service life than the modules themselves.

The inverter is the weakest link. In a well-managed roof lease contract it will have been replaced at least once — but this must be documented. If no maintenance history is available a technical audit is mandatory.

Why thermography before the takeover is indispensable

A visual inspection reveals glass breakage, discolouration and obvious mechanical damage. It does not show what is happening inside a module: hotspots from defective cells, PID degradation from voltage corrosion, failed bypass diodes or thermal anomalies at DC connectors.

This is precisely where the thermographic inspection is irreplaceable. A drone with an infrared camera surveys all modules and maps their heat distribution during operation. Defective cells and strings generate locally elevated temperatures — visible in the thermogram as bright spots. Analysis to IEC TS 62446-3 classifies every finding by severity and provides recommended actions.

What a complete takeover inspection involves

For a well-founded takeover decision we recommend a three-stage inspection covering all relevant system components:

Stufe 1: Drohnen-Thermografie aller Module

Full-coverage drone survey with IR camera at adequate solar irradiance (minimum 500 W/m²). Classification of all findings to IEC TS 62446-3. Result: detailed thermography report with module map, findings list and cost estimate for remediation.

Stufe 2: Elektrische Prüfung (DGUV Vorschrift 3)

Measurement of open-circuit voltage, short-circuit current and insulation resistance per string. Verification of all DC connectors for corrosion and contact resistance. Visual inspection of cable routing and junction boxes. Documentation as a measurement log per DGUV regulation 3.

Stage 3: inverter check and BOS inspection

Deep check of the inverter: transformer stages, capacitors, fans, display errors, log data from recent operating years. Inspection of BOS components (generator junction box, DC disconnector, feed-in point). Comparison of actual feed-in with theoretical expected performance using the performance ratio.

Takeover, renegotiation or dismantling — how to decide?

The thermography and inspection report provides the data basis. Building on this there are three sensible scenarios:

Szenario A: Übernahme lohnt sich

Fewer than 5% of modules with Class 2 or Class 3 hotspots, inverter in good condition or recently replaced, performance ratio above 75%. In this case the takeover is economically attractive. The system will produce electricity free of charge for another 15–20 years or can be sold for a fraction of its new value.

Szenario B: Nachverhandlung auf Basis des Befundberichts

Significant defects present but system fundamentally remediable. The findings report as a basis for negotiation: the investor must either remedy the defects before handover or the lessor accepts the takeover at reduced terms (e.g. the investor covers the cost of inverter replacement).

Szenario C: Rückbau verlangen

System is technically and economically at end of life – too many defective modules, inverter beyond repair, feed-in declining for years. In this case it makes more sense to call on the contractually guaranteed free dismantling by the investor and then plan a new, high-performance system.

Overview of advantages and disadvantages of the takeover

The decision for or against the takeover cannot be made on technical data alone. The economic and operational situation of the lessor also plays a role. The following comparison summarises the most important arguments:

Anyone currently facing the question of whether to lease their building roof at all will find at specialised providers such as on the platform dachverpachten.net an overview of current remuneration models, contract terms and legal protection through land register entries. The range on offer there — from one-off payment to annual lease to free roof renovation — directly determines how attractive the final phase with the 1-euro clause will be later.

Tax and insurance aspects of the takeover

With the transfer of the system to the ownership of the building owner new tax and insurance obligations arise that are frequently underestimated.

Income tax and § 3 no. 72 EStG

Since the Annual Tax Act 2022, income from photovoltaic systems up to 30 kWp on single-family homes or 15 kWp per residential or commercial unit on multi-family and mixed-use buildings is income-tax-free. Larger systems — the typical case for roof leases with roof areas from 500 m² — remain subject to trade and income tax. When taking over an existing system the lessor must register a business or adapt the existing commercial activity.

VAT and zero tax rate

The zero VAT rate applicable since January 2023 on the supply and installation of PV systems applies only to new systems, not existing ones. When taking over for the symbolic €1, regular 19% VAT applies to the actual fair market value of the system, provided the previous investor was entitled to input tax deduction. Careful tax advice in advance is indispensable here.

Versicherungsschutz

During the lease term the system is insured under the investor's operator liability — typically with a cover of €5–10 million. With the takeover this protection lapses and the lessor must take out their own insurance: PV insurance against storm, hail, fire and theft, plus operator liability for possible damage to third parties (e.g. if a module falls from the roof). Insurers frequently require a current thermography report for existing systems as a prerequisite — without a findings report there is no or only limited cover.

Determining residual value: replacement value, book value or income value?

For a takeover for own operation or a subsequent resale a formal valuation makes sense. Unlike for real estate there is no uniform statutory valuation method for photovoltaic systems — in practice four value concepts have established themselves that are applied depending on the purpose of the valuation:

For the takeover of a roof-lease system at the 1-euro purchase price the primary consideration is the Ertragswert : how much electricity income will the system still generate in the remaining 10–15 years, and how high are the expected maintenance and repair costs? The replacement value only matters when you want to insure the system against hail, storm or fire.

A standards-compliant thermography report to VdS 2858 forms the technical basis for each of these valuation methods — it documents the actual condition of the system at the time of handover and is usable for insurers, financiers and tax purposes. More on methods and factors of PV system valuation in unserem ausführlichen Ratgeber.

Übergabe-Checkliste: Diese Dokumente brauchen Sie

When the operator changes from investor to building owner it is not just about the physical system — the vollständige Dokumentation must also be handed over. Missing commissioning documentation can later cause problems for insurance claims, warranty claims or a resale. The following documents should be part of the handover:

Technische Dokumentation

• Anlagenpass with an overview of all components, module types, inverter models and serial numbers
• Inbetriebnahmeprotokoll with date of initial commissioning and measurement log
• Stringplan and electrical wiring diagram of the system
• Modul-Datenblätter with performance class and manufacturer warranties
• Wechselrichter-Dokumentation einschließlich aller seitherigen Tauschvorgänge
• Statisches Gutachten of the mounting structure for roof load

Maintenance and inspection documentation

• E-Check-Protokolle per DGUV regulation 3 (on a 4-year cycle)
• Thermografie-Berichte aus den vergangenen Wartungszyklen
• Maintenance and service history with all work carried out
• Reparaturhistorie with evidence of replaced components

Legal and administrative documents

• Eintragung im Marktstammdatenregister (MaStR) of the Federal Network Agency — must be re-registered within one month, otherwise fines may be imposed and the grid operator can withhold the feed-in tariff
• Einspeisevertrag with the responsible grid operator
• EEG-Meldedaten and subsidy notice with remaining term
• Versicherungsunterlagen of the previous operator's insurance
• Grundbuchauszug with deletion of the limited personal easement

What happens after the takeover: continued operation options

With the takeover for €1 the old contractual relationship ends — and for the system a new phase begins, often referred to as Post-EEG-Anlage oder ausgeförderte Anlage . For systems commissioned in the 2000–2002 period the EEG subsidy has already expired. For systems from 2008 onward the 20-year subsidy is expiring in the coming years — which practically means: the takeover after 25 years of lease typically meets a system without an active EEG tariff. Three continued-operation models are currently economically attractive:

Option 1: Eigenverbrauch des Solarstroms

The generated electricity is consumed directly in one's own building — as hall power, for production facilities, office lighting or charging electric vehicles. At electricity prices of 25–35 ct/kWh and self-consumption rates from 40% this option is almost always worthwhile. Self-consumption can be optimised with a storage system or intelligent load shifting (e.g. heat pump operation during the day).

Option 2: Other direct marketing at market value

Surplus electricity is sold on the electricity exchange via a direct marketer. The remuneration is based on the monthly solar market value — typically 4–8 ct/kWh, and considerably more in periods of high electricity demand. This option now replaces the classic EEG feed-in tariff for systems that have left the support scheme and has been legally regulated for existing systems since 2021.

Option 3: Power Purchase Agreement (PPA)

A long-term electricity offtake contract with an industrial customer, a regional utility or an energy trader. Advantage: plannable revenues over 5–15 years. Disadvantage: requires minimum volumes and is usually not economical for smaller systems below 100 kWp.

Which option is worthwhile depends on the self-consumption potential of the building. Rule of thumb: anyone who can consume more than 40% of the produced electricity themselves should seriously consider the self-consumption option — it generally delivers the highest return. For the remaining portions other direct marketing makes sense, which the direct marketer handles largely on an administrative basis.

Frequently asked questions