Example: Deduction for improvement works to reduce heating and cooling demand

The married couple Mr. JP and Mrs. RL, married under the legal regime of community property, carried out on June 27, 2025 in their usual residence the replacement of all the windows (frame and glazing) with double windows to achieve greater efficiency in the thermal insulation of the home for a total amount of 8,900 euros which were made effective on June 30, 2025 by bank transfer.

To replace the windows, he requested and received a grant from his Autonomous Community of residence amounting to 1,500 euros.

In addition, in another rented property he owns, he changed the gas boiler to a biomass one during the month of December, which represents an energy saving of 13%. The total cost of the new boiler amounts to 3,500 euros, which were paid on December 15, 2025.

To prove compliance with the requirements for this deduction, an energy efficiency certificate was requested for both homes before and after the works.

In their usual residence, a certificate was issued on May 15, 2025, which was registered in the corresponding registry (before the works) and another on July 22, 2025 (registered on November 25, 2025), resulting in a 20 percent reduction in the sum of the heating and cooling demand indicators of the energy efficiency certificate issued by the competent technician. The certificates cost 100 euros.

In the case of the rented property, there was an energy efficiency certificate less than two years old and after the boiler was changed in December 2025 a new certificate was issued on December 30, 2025 for the amount of 80 euros which certifies the aforementioned savings of 13 percent.

Determine the amount of the deduction for 2025 in individual and joint taxation.

Solution:

Please note that Royal Decree-Law 16/2025, of December 23, extends certain measures to address situations of social vulnerability and adopts urgent measures in tax and social security matters (BOE of December 24) has modified the time frame of the deductions for energy efficiency improvement works in homes regulated by the fiftieth Additional Provision of the Law of IRPFABBR, extending it in the case of this deduction until December 31, 2025.

Contributor Mr. JP .

Deduction base: 5.500

8,900 euros (works) + 3,500 (boiler) + 100 euros (certificates) – 1,500 euros (aid obtained) ÷ 2 = 5,500 euros

Please note that the subsidies derived from the Renove Plan for window replacement in the different Autonomous Communities are generally obtained by the beneficiaries in the form of a discount that is applied to the invoice for the acquisition and installation of the goods by the collaborating entities of the program, which process the subsidy on behalf of the beneficiary, applying it to the invoice as an advance payment to the beneficiary.
Maximum deduction base: 5,000 euros
Deduction amount: (5,000 x 20%) = 1,000

Taxpayer Mrs. RL .

Deduction base: 5.500

8,900 euros (works) + 3,500 (boiler) + 100 euros (certificates) – 1,500 euros (aid obtained) ÷ 2 = 5,500 euros
Maximum deduction base: 5,000 euros
Deduction amount: (5,000 x 20%) = 1,000

Joint statement by Mr. JP . and Mrs. RL

Deduction base: 11,000

8,900 euros (works) + 3,500 (boiler) + 100 euros (certificates) – 1,500 euros (aid obtained) = 11,000 euros
Maximum deduction base: 5,000 euros
Deduction amount: (5,000 x 20%) = 1,000