Energy classes A-G of a building: what they mean for owners and buyers

When you look for a home to buy or rent, the listing almost always shows a letter from A to G, accompanied by the phrase "energy class". For many buyers, that letter remains an abstract detail, somewhere next to the floor area and the floor number. In reality, it summarises a technical document — the energy performance certificate (CPE) — which states how much energy the building consumes for heating, hot water, ventilation and, where applicable, cooling, and what can be done to reduce that consumption.

What the energy class is and why it matters

The energy class is the result of a regulated calculation, carried out by an attested energy auditor, in which the building or apartment is assessed in terms of the annual primary energy consumption needed for it to operate at normal comfort parameters. The result is expressed as one of the eight classes (Mc 001-2022, table 5.7) — from A+, for the buildings with the lowest consumption, close to the standard of nearly zero-energy buildings (nZEB), to G, for the buildings with the highest consumption, usually old, uninsulated constructions or ones with inefficient installations.

For an owner or a buyer, the energy class is not just an administrative formality. It has two direct and measurable effects:

• Monthly utility costs. A building in the lower classes (F, G) consumes visibly more energy for the same floor area and the same level of comfort than one in the higher classes. The difference shows in the gas, electricity or heat bills, month after month, for as long as you live there.
• The market value of the property. As energy bills have become an increasingly visible criterion in the buying decision, a good energy class has become a selling point, while a poor one is a reason to negotiate the price or to postpone the transaction, especially if the thermal rehabilitation work required is visible or costly.

How to read an energy performance certificate

A CPE issued under the current methodology (Mc 001-2022, approved by Order MDLPA no. 16/2023) contains, besides the identification data of the building and of the auditor who issued it, a few elements worth looking at:

1. The energy class, displayed visually on the A-G scale — the quickest piece of information to read at a glance. 2. The consumption indicator, that is, the calculated value of the building's energy consumption, which underlies the assignment to a class. It is the technical figure behind the letter. 3. The recommendations for improving energy performance — a section in which the auditor lists, usually in order of cost-benefit efficiency, the measures that could raise the building to a higher class (for example insulating the envelope, replacing windows and doors or modernising the heating system). 4. The period of validity and the date of issue, visible on the certificate.

The recommendations are not mandatory to follow — the certificate describes the current state of the building and the theoretical possibilities for improvement; it does not impose any particular work.

The legal obligation at sale and lease

In Romania, the mandatory CPE in real estate transactions is regulated by Law no. 372/2005 on the energy performance of buildings, republished. Under art. 22 para. (1) of the law, for buildings or building units that are sold or leased, the owner (or the investor/administrator, as the case may be) is obliged to make a copy of the certificate available to the potential buyer or tenant, before the contract is concluded. On completion of the sale, the owner is obliged to hand over the certificate, in the original, to the new owner (art. 22 para. 2).

The certificate is valid for 10 years from the date of issue entered on the document, except where the building undergoes major renovation work that changes its energy performance — in which case a new assessment is required (art. 21 para. 2 of the same law).

The law also provides for consequences for failing to meet these obligations. Sale and purchase contracts concluded without the potential buyer having received a copy of the certificate are subject to relative nullity (art. 22 para. 4). In addition, art. 36 para. (1) lit. m) of Law 372/2005 republished (in the consolidated form, after Law 238/2024) penalises as a contravention the failure to comply with art. 24, that is, stating in sale or lease advertisements the information from the certificate on the performance indicators, with a fine of 5,000 to 7,500 lei (art. 36 para. (3) lit. a). Beyond these consequences, the lack of a valid CPE can delay or complicate a transaction, especially when the buyer or the financing bank asks for the document as part of the file.

What an owner can do to move up an energy class

There is no universal recipe — each building has a different profile of energy losses, and the recommendations in the CPE reflect exactly its situation. Broadly, the measures that appear most often in certificates issued for buildings in the lower classes fall into three areas:

• Building envelope — thermal insulation of the exterior walls, of the floor over the top storey and, where applicable, of the plinth or basement. This reduces heat loss through the opaque surfaces of the building.
• Exterior windows and doors — replacing old windows and doors, with poor thermal performance, with modern, airtight ones.
• Technical systems — modernising the heating installation and the domestic hot water preparation system, or introducing renewable energy sources, where feasible.

Each of these interventions has a different cost and impact, and the order in which they are worth tackling depends on the specific recommendations in the certificate, not on a generic list. That is why talking to the auditor who issued the CPE — or to a new one, if you intend extensive works — is the step most often missing from owners' decisions.

How to choose an attested auditor

Energy certification and auditing of buildings are carried out exclusively by energy auditors for buildings attested by the ministry, under art. 30 para. (1) of Law 372/2005 republished. In practice, a CPE cannot be validly issued by anyone other than an auditor who holds this attestation in active status. When choosing an auditor, it is useful to check:

• that the attestation is active and corresponds to the category of building you own (some professional grades have broader competences than others);
• prior experience with buildings similar to yours in type and age;
• the clarity of the explanations they give you about the consumption indicator and the recommendations in the certificate — a well-made certificate should be easy to understand, not just to show to the notary.

For the technical part of the calculation and the generation of documents, many attested auditors in Romania use the Zephren calculation program, built specifically for preparing energy performance certificates under Mc 001-2022. It is a working tool for auditors, not a certification service for owners — but if you want to understand what stands behind the calculation your auditor presents to you, it is worth knowing that it exists.