How the DGT's position has evolved
Current position
To qualify for the 20% deduction, heating and cooling demand must be reduced by at least 7%. The deduction is applied in the tax period in which the certificate issued after the works is released, although it may be claimed in the year of payment if the certificate is issued in a subsequent year. Certificates issued before the start of the works are valid if no more than two years have passed between their issuance and the start of the works.
Automatic analysis was unable to anchor the milestones to the available criteria. The DGT's position appears consistent within the corpus.
Analysis based on 26 of 26 rulings with a stated position. Updated 24 September 2026.