Short answer
What you need to know first.
In Canton Solothurn, PV investments on existing buildings may be deductible as an energy-saving and environmental-protection measure. For new builds and replacement new builds, the 5-year boundary applies; only owner-borne costs are deductible, not amounts covered by EIV or other contributions. Invoice date, actual-cost deduction and complete evidence are decisive.
Important
As of 2026, this classification concerns private properties in Solothurn and the standard cases described in the tax manual. New buildings within the first five years, systems on third-party roofs, business assets, contracting models and mixed-use buildings can be treated differently for tax purposes and should be checked with the competent tax office or adviser before implementation.
Decision points
What determines the right path.
The most important factor is the building age. The Solothurn tax manual treats new builds, replacement new builds and buildings completed within the last five years as non-deductible investments for income tax; the costs borne by the owner instead increase the investment costs for later real-estate gains tax.
For existing buildings, the deduction is tied to § 6 para. 1 StVO No. 16 and Art. 5 LKV: costs for measures that improve rational energy use or use renewable energy can be deducted for income tax. According to the tax manual, this also includes photovoltaic systems on or attached to existing buildings.
The flat-rate deduction blocks the PV costs. The tax manual states that energy-saving and environmental-protection measures are only considered under the actual-cost deduction; anyone choosing the flat-rate property-cost deduction cannot additionally claim the PV investment.
Incentives change the tax calculation. If the investment costs are deductible, subsidies and investment aid including the Pronovo EIV are taxed as other income; if they are not deductible because of new-build status, the contributions reduce the investment costs.
Battery storage is not generally excluded in Solothurn. Following the tax court decision of 23 May 2022, storage units combined with renewable energy generation count as deductible energy-saving and environmental-protection measures, except for new buildings during the first five years.
For feed-in payments, Canton Solothurn applies the net principle. The payment for exported electricity is taxed only to the extent that it exceeds the cost of electricity purchased from the grid; according to the tax manual, self-consumed PV electricity does not increase the imputed rental value.
Sequence
How the project stays cleanly managed.
- 1
Classify the building for tax purposesbefore the quote, check whether the property is an existing building or whether new-build, replacement-new-build status or the 5-year boundary from the Solothurn tax manual applies. This classification decides whether the deduction matters for income tax or only through investment costs.
- 2
Prepare cost positionshave quotes and invoices separated by PV system, battery storage, bidirectional charging station, installation, electrical work and any roof work. The tax manual requires a traceable schedule for actual property costs; individual amounts from CHF 500 must be supported by invoice copies.
- 3
Keep incentives separaterecord Pronovo EIV and any municipal or cantonal contributions separately from gross costs. In Canton Solothurn, building-programme funding applications must be submitted before construction starts; Pronovo EIV for PV runs through Pronovo, not through the cantonal energy office.
- 4
Plan the deduction yearunder the Solothurn tax manual, the invoice date is generally decisive. If energy-saving and environmental-protection measures cannot be fully used in the invoice year because net income is negative, the remaining costs can be carried forward to two following tax periods.
- 5
Look at feed-in on a net basiscollect grid electricity costs and feed-in payments for the same tax year. Under Solothurn’s net principle, the feed-in payment is only taxed to the extent that it exceeds the cost of grid electricity purchased; whether the grid operator nets the amounts is not decisive.
- 6
Document the tax returnwhen claiming actual property costs, submit invoices, funding decisions, statements and, where useful, photos of the condition before and after the measure. For mixed works, the tax office may require an allocation between value-preserving and value-increasing portions.
Checklist
Questions to settle before the quote.
- Is the building older than five years or still treated as a new build for tax purposes?
- Is claiming actual property costs more sensible than the flat-rate deduction?
- Are Pronovo EIV, municipal contributions and invoices documented separately?
- Does the Solothurn net principle create taxable income from the feed-in payment at all?
FAQ
Common questions on this topic.
Sources
Official sources & references.
The responsible authorities are decisive. Always verify binding details – amounts, deadlines and conditions – for your specific property against the current status of the respective authority.