Sonder-AfA and Investitionsbooster 2026 for PV Systems

Two instruments accelerate the depreciation of commercial PV systems in 2026: the Sonder-AfA (special depreciation under § 7g (5) EStG) at 40% and the 30% per year declining balance depreciation of the Investitionsbooster (Germany's 2025-2027 accelerated depreciation package). Both have deadlines, both have conditions, and the order in which they are applied in the tax toolkit determines the effect.

Instrument 1: Sonder-AfA under § 7g (5) EStG

For acquisitions since January 1, 2024, the special depreciation amounts to 40% of the acquisition costs (previously 20%). The key points:

• Freely allocable over five years: the 40% can be claimed entirely in the year of acquisition or spread out, on top of regular depreciation.
• Same conditions as the IAB: profit of no more than €200,000 in the year before acquisition, at least 90% business use, and the asset must remain in the business until the end of the following year.
• Can be combined with the Investitionsabzugsbetrag (IAB, Germany's investment deduction): if an IAB was claimed beforehand, the Sonder-AfA is calculated on the acquisition costs reduced by the IAB.

Instrument 2: The Investitionsbooster (30% declining balance depreciation)

With the immediate investment program of July 2025, movable assets acquired between July 1, 2025 and December 31, 2027 once again qualify for declining balance depreciation: up to 30% per year of the remaining book value.

For a PV system this means: 30% in the first year, 30% of the remainder in the second, and so on, with a later switch to straight-line depreciation once that becomes more favorable. Compared with straight-line depreciation over 20 years (5% per year, see depreciation for photovoltaics), this shifts the tax relief massively forward.

The deadline is the essential point: what counts is the transfer of beneficial ownership, or operational readiness, by the end of 2027. With project timelines of several months including grid connection, 2026 is the year in which the decision has to be made, not 2027.

What can be combined, and how

The stages of the toolkit, in the order of their effect:

1. IAB in the planning year: up to 50% of the expected costs, capped at €200,000 (calculator).
2. At acquisition: 40% Sonder-AfA on the reduced assessment base, freely spread over five years.
3. In parallel: regular depreciation, straight-line or declining balance (mind the Investitionsbooster window).

Whether combining the Sonder-AfA with declining balance depreciation is permissible and sensible in a specific case belongs in the hands of a tax advisor; the instruments come from different legislative packages, and the detailed rules (§ 7a EStG) are not a self-service shelf.

Context: Why the window matters

Tax instruments are no substitute for project quality: a system that does not pay off without the depreciation effect will not pay off with it either. But for companies whose PV project is economically sound in its own right (the numbers), the 2026/2027 window shifts the after-tax return significantly. The project roadmap: clarify feasibility and grid connection now, claim the IAB in the right year, complete the acquisition before the booster window closes. Start your project: analysis in NEXA ONE