Background
#In the canton of Basel-Stadt, expenses for measures that contribute to rational energy use or renewable energy are deductible from income for existing private buildings, even if they add value.
The tax administration’s factsheet lists photovoltaic systems in existing buildings, including design and preparatory work, as an energy-saving measure with a deduction rate of usually 100 percent. For new builds and within two years of their completion, these costs belong to capital costs. No deduction is possible to the extent subsidies are received.
The tax period in which the costs were paid is decisive. This page summarises published practice and does not replace an assessment of your case.
For your roof
What the deduction means for your home
The report for your address combines the one-off payment, cantonal incentives and tax deduction, with net investment and payback.
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What drives the economics
#Deduction for existing buildings: under the factsheet on deducting property costs (edition of 1 January 2026, valid for cantonal and federal tax), both value-preserving and value-adding expenses for energy-saving measures are deductible when they replace outdated components or install new ones for the first time in existing private buildings. The catalogue lists photovoltaic systems including design and preparatory work on the property under section 6.12.
Two years after a new build: energy-saving and environmental measures on new builds are always attributed to capital costs. This also applies to investments made close in time, meaning within two years of the new build’s completion.
Subsidies and the flat rate exclude the deduction: no deduction is possible to the extent subsidies are received for the measure. Nor is a deduction possible if the flat rate is claimed instead of actual costs. Subtract incentives such as the one-off payment from the costs before comparing flat rate and actual costs.
Flat rate by building age: the flat-rate deduction is 10 percent of the imputed rental value if the building is no more than ten years old at the start of the tax period, otherwise 20 percent. You can switch between flat rate and actual costs in every tax period (2025 tax guide).
The payment date decides: in Basel-Stadt, property costs are deductible in the tax period in which they were paid. Energy-saving and environmental investments that cannot be fully taken into account can be carried forward to the two following tax periods, provided they were declared in the period of the payment date.
Feed-in and wealth tax: payments from feed-in remuneration or direct marketing of electricity are taxable income. Neither the factsheet nor the tax guide mentions offsetting against electricity costs; clarify this with the tax administration. For non-commercial, self-used and insured rooftop systems, the property’s wealth-tax value is reduced on application by the insured value or a flat CHF 15,000.
From 2029 the Confederation changes the system: with the change in residential property taxation, the federal maintenance deduction for owner-occupied homes falls away from 1 January 2029. Cantons may provide energy-saving deductions until 2050 at the latest (Art. 78h StHG); check with the tax administration how Basel-Stadt will handle this.
The process in five steps
#Tick off for your project
Record the building’s age
note the completion date. Within two years after that, solar systems count as capital costs and no deduction is possible.
Compare costs and incentives
have the system, design and preparatory work itemised and subtract subsidies received. Only the self-borne part is deductible.
Time your payments
the payment date counts. Record which invoice you pay in which tax period and declare the costs in exactly that period.
Choose the method
compare the 10 or 20 percent flat rate with actual costs. In the installation year, actual costs usually win because the flat rate excludes the energy deduction.
Record income and assets
declare feed-in payments under other income and clarify whether electricity costs can be credited. For a self-used, insured rooftop system, apply for the reduction of the wealth-tax value.
Checked for your roof, not just read up on
What the deduction means for your home
The report for your address combines the one-off payment, cantonal incentives and tax deduction, with net investment and payback.
Free and non-binding · no unsolicited calls
Rather talk directly? +41 78 615 90 58
Frequently asked questions
#Sources
#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.