As of August 12, 2025, banks require an energy efficiency certificate to appraise mortgages. Effective July 23, 2026, Royal Decree 659/2025 has updated the regulatory framework regarding who can issue the certificate and how it must be validated. And effective September 30, 2026, the new forms for certificate, the updated labels, and the electronic format. The energy performance certificate is no longer just a one-time formality: it is a document that affects the sale, rental, mortgage, and eligibility for renovation grants.
For professionals in the fields of construction, engineering, and architecture, this is also an opportunity: the demand for qualified certifiers is growing, and the regulations have just expanded access to new professional roles.
What is an energy efficiency certificate, and what is it used for?
The Energy Efficiency Certificate is a an official document that assesses how much energy a building or home consumes under normal conditions of use It includes a label that rates the property on a seven-letter scale, from A (most efficient) to G (least efficient). It takes into account indicators such as non-renewable primary energy consumption and CO₂ emissions resulting from the building’s use, including heating, cooling, ventilation, domestic hot water, and lighting.
Beyond being a mere administrative formality, the certificate has a real and growing impact on a property’s value: a home with a D or E rating may be worth significantly less than an equivalent home with a B rating, and that difference will widen in the coming years as the requirements of the European Energy Performance of Buildings Directive become more stringent.
Is it mandatory? Cases in which the law requires it
This requirement is governed by Royal Decree 390/2021, as amended by Royal Decree 659/2025. The certificate is required in the following cases: newly constructed buildings, which the developer or builder obtains prior to delivery to the buyer; existing buildings that are sold or rented; buildings that are required to undergo a technical inspection or have a building assessment report prepared; and certain nonresidential buildings larger than 500 square meters. Failure to comply may result in fines of up to 6,000 euros.
Existing and valid certificates do not need to be renewed due to the 2026 regulatory change unless significant renovations are carried out or a specific circumstance provided for in the regulation arises.
Who can issue an energy efficiency certificate?
This is the major change introduced by Royal Decree 659/2025, which took effect on July 23, 2026. Qualification is no longer based solely on a university degree. The regulations now distinguish between two types of certificates:
For certificates for buildings under construction, The right to sign off on such documents remains reserved for professionals who are legally authorized to draft building plans or supervise construction projects: architects, engineers, or technical architects.
For certificates for existing buildings or completed construction projects, The new regulation expands access to other professional profiles that can demonstrate they have the necessary specific training by submitting a sworn statement to the competent regional authority, which is then recorded in the new Centralized Administrative Registry of Qualified Technicians.
How is a building's energy rating calculated?
The certification process begins with the collection of data on the building (building envelope, HVAC systems, facilities, orientation, and geographic location) and their input into officially recognized software tools, such as CE3X or Cypetherm HE Plus. The software calculates non-renewable primary energy consumption and CO₂ emissions and generates the rating. The interactive tool below provides a rough estimate based on the building’s main characteristics:
Factors That Most Influence the Final Grade
The factors that have the greatest impact on the rating are the level of thermal insulation of the building envelope (facades, roof, and floor), the efficiency of the heating and cooling system, the energy source used (gas, grid electricity, geothermal energy, biomass) and the building's orientation. A home with good building envelope but an inefficient HVAC system may receive a D or E rating even if it appears to be well-built.
Energy Certificate vs. Energy Audit: Differences
The energy certificate assesses the building's current condition and assigns it a rating. The energy audit goes one step further: It analyzes actual energy consumption in detail, identifies the causes of energy waste, and proposes improvement measures along with estimates of savings and return on investment. According to the Energy Efficiency Directive, energy audits are mandatory for large companies (those with more than 250 employees or more than 50 million euros in revenue) every four years. For most residential and commercial buildings, the certificate is sufficient to comply with the regulations.
How to Become a Specialist in Energy Certification
The demand for qualified certification technicians is growing in Spain at the same pace as energy retrofit requirements become more stringent. The new regulatory framework opens the door to professionals who previously could not enter this field, provided they can demonstrate that they have completed the required specific training.
