Background
#In the canton of St. Gallen, investments that save energy and protect the environment are treated like maintenance costs to the extent they are deductible for the direct federal tax (Art. 44(2) StG).
The catalogue in the St. Gallen tax manual lists installing a photovoltaic system on your own roof and a battery as fully deductible energy-saving investments. If the system is installed within two years of a new build, it counts as capital cost. Grants received reduce the deduction, and income from electricity generation must be declared as other income to the extent it exceeds self-consumption. This page summarises the published guidance 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
#The rule follows federal law: under Art. 44(2) StG and StB 44 no. 5, whether an expense serves energy saving and environmental protection is determined by the law on the direct federal tax. Measures in existing buildings are deductible, meaning replacement of outdated or first-time installation of new components and installations.
The catalogue is specific: StB 44 no. 3 (as of 1 January 2026) lists installing a photovoltaic system on your own roof and installing a battery as 100 percent deductible energy-saving investments. A mobile photovoltaic system counts as private expenditure, and installing an EV charging station as non-deductible capital cost.
Two years after a new build: energy-saving and environmental investments in new builds count as capital costs, even if made after occupation but in a project-related connection with the new build. If more than two years pass between completion of the new build and the investment, the tax office treats the building as existing (StB 44 no. 5, section 6).
Grants reduce the deduction: for property held as a private asset, deductible energy-saving measures must be reduced by grants received from the canton, municipality and third parties (StB 44 no. 5, section 9). This affects incentive programmes as well as the one-off payment for your system.
Flat rate or actual costs: for property mainly used for housing, the flat-rate deduction for cantonal tax is 20 percent of the imputed rental value or gross rental income (StB 44 no. 8). It also covers energy-saving measures; if you choose the flat rate, you cannot deduct the solar system on top. The choice applies per tax period and property.
Timing and carry-forward: expenses are deductible at the time of invoicing. If they cannot be fully taken into account in that period because net income is negative, they are carried forward to at most two following periods; free allocation is not possible. Forgotten energy-saving costs cannot be claimed later against property gains tax (StB 44 no. 5).
Electricity income and 2029: the 2025 tax guide lists income from photovoltaic electricity generation as other income to the extent it exceeds self-consumption. From 1 January 2029, the federal maintenance deduction for owner-occupied homes also falls away; cantons may provide energy-saving deductions until 2050 at the latest (Art. 78h StHG). Check with the cantonal tax office how St. Gallen will implement this.
The process in six steps
#Tick off for your project
Check the building’s age
record when the new build was completed. If less than two years lie between completion and investment, expect capital costs instead of a deduction.
Separate items according to the catalogue
have the photovoltaic system, battery and charging station listed separately. System and battery are deductible under StB 44 no. 3, the wallbox is not.
Subtract grants
reduce the costs by the one-off payment and grants from the canton, municipality or third parties. The self-borne remainder stays deductible.
Choose the method
in the invoice year, compare actual costs with the 20 percent flat rate. With the flat rate, the solar system deduction falls away.
Keep evidence ready
expenses are deductible at the time of invoicing and the burden of proof is yours. Keep invoices and the incentive decision in order.
Declare electricity
collect your grid operator’s statements and declare income from electricity generation, to the extent it exceeds self-consumption, under section 6.3 of the tax return.
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.