La influencia de los incentivos fiscales en la construcción sostenible

Tax incentives for sustainable construction operate through four main mechanisms: income tax deductions (personal income tax or equivalent), local tax rebates (property tax, construction tax), transferable tax credits, and accelerated depreciation of green investments. In the European Union, 24 of the 27 member states offered some type of tax incentive for building energy efficiency in 2023, with an estimated combined fiscal expenditure of 18 billion EUR annually (European Commission, DG TAXUD, 2023). The most widespread mechanism is the personal income tax deduction for energy retrofit works, available in 19 EU countries with deduction rates ranging from 15% (Germany, since 2020) to 110% (Italy, Superbonus 110% between 2020 and 2023). In Spain, Royal Decree-Law 19/2021 established three temporary personal income tax deductions for improving residential energy efficiency: 20% for reducing heating and cooling demand by at least 7%, 40% for reducing non-renewable primary energy consumption by at least 30%, and 60% for energy retrofit of residential buildings achieving an energy rating improvement to class A or B, with maximum bases of 5,000, 7,500, and 15,000 EUR respectively.

Local taxes offer a second incentive channel. In Spain, 1,847 municipalities (22.8% of the total) offered property tax (IBI) rebates in 2023 for buildings with energy certification A or B or with solar installations, with discounts of 20-50% for 3-5 years (Fundación Renovables, 2023). Madrid applies a 50% property tax rebate for 3 years for self-consumption photovoltaic installations and 25% for buildings with an energy rating of A. Barcelona offers a 50% rebate on the Construction Tax (ICIO) for works incorporating solar energy systems. At the European level, the most developed model is that of the Netherlands, where the real estate transfer tax (Overdrachtsbelasting) is reduced from 10.4% to 2% for homes with an energy rating of A, generating average savings of 12,000-25,000 EUR per transaction that incentivize both the purchase of efficient homes and pre-sale renovation.

The Italian Superbonus 110% constitutes the largest fiscal experiment to stimulate energy retrofit in the history of the EU. Implemented between July 2020 and December 2023, it allowed deducting 110% of the cost of works that improved the energy rating by at least 2 classes, with the option to transfer the tax credit to financial institutions or receive an invoice discount. The program mobilized 114 billion EUR of investment in 480,000 residential buildings, benefiting 4.7 million dwellings (ENEA, 2024). The documented average energy improvement was 2.5 classes on the Italian scale (A-G), and the average energy consumption reduction per retrofitted dwelling was 51%. However, the fiscal cost was massive: 125 billion EUR in tax credits issued, 5.6% of Italian GDP, which contributed to raising the public deficit to 8.8% of GDP in 2023 and generated a GDP revision by Istat that revealed that 10-15% of credits were linked to fraud or cost overruns (Corte dei Conti, 2023).

More moderate programs show better cost-effectiveness. The German energy retrofit program BEG (Bundesförderung für effiziente Gebäude), which combines direct subsidies of 15-25% with tax deductions of 20% spread over 3 years, mobilized 28 billion EUR of investment in 2022 with public spending of 7.2 billion EUR, a leverage ratio of 1:3.9 (BMWK, 2023). France allocates 4 billion EUR annually to MaPrimeRénov', an income-graduated direct subsidy program that funded the retrofit of 670,000 dwellings in 2022, with a documented average energy saving of 32% per dwelling (ANAH, 2023). In the United States, the Inflation Reduction Act of 2022 allocated 369 billion USD over 10 years to the energy transition, including the expanded 45L tax credit that grants 2,500-5,000 USD per multifamily dwelling meeting ENERGY STAR or Zero Energy Ready standards and the 179D credit that allows deducting up to 5 USD/ft² (equivalent to 54 USD/m²) for energy retrofit of commercial buildings reducing consumption by 25% compared to ASHRAE 90.1.

Empirical evidence demonstrates that tax incentives accelerate the adoption of sustainable building standards in measurable ways. A study by Giraudet et al. (2021), published in Energy Economics, analyzed the effect of the French tax credit (CITE) on 1.2 million tax returns between 2005 and 2018 and found that each additional 1,000 EUR in tax credit increased the probability of undertaking an energy retrofit by 12% and the average spending of households that did retrofit by 8%. The price elasticity of retrofit investment was -0.6: a 10% reduction in net cost (via tax deduction) generated a 6% increase in investment. The leverage ratio of public investment varies by incentive design: programs with greater selectivity (targeting dwellings with the worst energy ratings and lower-middle income households) achieve ratios of 1:5 to 1:7, while universal programs like the Italian Superbonus yield 1:0.9 (the public cost exceeds the incremental net investment because many retrofits would have occurred anyway without the incentive, a phenomenon known as the deadweight effect).

In the office building market, tax incentives combined with ESG demand have transformed the investment structure. Real estate investment trusts (REITs) that obtain BREEAM or LEED certification for their assets access green financing (green bonds, green loans) with spreads 15-30 basis points lower than conventional financing (Climate Bonds Initiative, 2022). In Spain, Merlin Properties estimated that the BREEAM certification of its office portfolio (1.4 million m²) reduced its average financing cost by 18 basis points, equivalent to 4.2 million EUR annually in interest savings (Merlin Properties, ESG Report, 2023). The tax deduction for sustainability investments under Spain's Corporate Income Tax allows deducting 12% of the cost of installations that improve energy efficiency in commercial buildings, with a limit of 25% of the gross tax liability. Colonial, another major Spanish REIT, documented that tax deductions covered 22% of the LEED Gold certification premium for its portfolio of 850,000 m² in Madrid and Barcelona (Colonial, Annual Report, 2023).

Accumulated experience enables the identification of design principles that maximize the impact of tax incentives. First, progressivity: scaling the incentive intensity according to the ambition of the improvement (higher deduction for achieving class A than for class C) and the beneficiary's income (greater assistance for vulnerable households) multiplies the effect by 2-3 times compared to flat incentives, according to the evaluation of MaPrimeRénov' by the French Cour des Comptes (2022). Second, temporality: incentives with an expiration date generate an anticipation effect that increases investment by 30-50% in the 12-18 months before expiry, but cause an equivalent subsequent drop (cliff effect), as demonstrated by the experience of the US residential renewable energy tax credit before each legislative renewal (Gillingham & Tsvetanov, 2019). Third, administrative simplicity: programs with integrated digital processing and automatic approval achieve utilization rates of 60-80% of potential beneficiaries, compared to 15-30% for programs requiring complex documentation and prior auditing (BPIE, 2022).

For the Spanish context, evidence-based recommendations include: extending the personal income tax deductions for energy retrofit beyond 2024 and raising maximum bases to 20,000-30,000 EUR for comprehensive retrofits achieving class A; establishing a national minimum property tax rebate of 30% for buildings with an energy certification of A, acting as a standard for the 77% of municipalities that currently offer no rebate; creating a reduced VAT rate of 4% (versus the current 10%) for certified energy retrofit materials and services, a measure that the European Commission has expressly authorized in Directive 2022/542 and already applied by Belgium, France, and Luxembourg. A study by CEPS (Centre for European Policy Studies, 2023) estimated that the combination of these three measures could increase Spain's retrofit rate from 30,000 dwellings/year (current figure) to 120,000-180,000, approaching the target of 300,000 dwellings/year needed to comply with the recast EPBD. The estimated fiscal cost would be 1.8-2.5 billion EUR annually, generating a return of 4.5-7 billion EUR in economic activity, employment (80,000-120,000 jobs), and cumulative energy savings.