An energy audit consists in performing a complete and detailed inventory of the energy performance of a building. It provides a work program or the installation of real estate measurement solutions. It allows to identify sources of energy savings and to forecast the costs related to a new renovation
The period of validity of the energy audit
For residentials with collective heating, an energy audit has been mandatory since 2013. This is an energy balance sheet that aims to classify the building, which can be the origin of a dpe (energy performance diagnosis). This classifies the building according to its energy expenditure. The results of the energy audit are then formulated in a report intended to present ways of improving energy efficiency. Under these conditions, the energy audit is valid for 10 years. The same applies to the energy performance diagnosis.
On the other hand, for companies subject to the mandatory energy audit, the period of validity of the certification linked to the performance of the energy audit is reduced to 4 years. At the end of this period, the energy audit must be renewed.
As a reminder, the mandatory or regulatory energy audit concerns companies with more than 250 employees, and/or with revenues of more than 50 million euros, and/or with balance sheets of more than 43 million euros. The audit must cover 80% of the company’s energy bill and include all types of energy used by the company (gas, electricity, biomass, coal, etc.).
Conducting an energy audit can have a positive impact on the application for a tax credit for work projects. It can also enable the company to obtain quality labels certifying its commitment to energy transition..

How long does it take the auditor to complete an energy audit ?
The time it takes to complete an energy audit depends on the particular case of the client. For companies, the conduct of an energy audit is mandatory from 250 employees, 50 million euros of turnover or 43 million euros of balance sheet. The only exception: companies holding ISO 500001 certification are exempt from mandatory energy audits. In addition, many companies with ISO 500001 certification have begun to implement an energy management system.
The size of the company and the scope of the audit vary significantly in terms of the duration of the energy audit and the nature of the studies carried out. Of course, the duration will not be the same for a single building as for several buildings. For the companies concerned by the mandatory audit, the scope must be at least 80% of the total energy bill. Other companies can choose to have their energy audit cover all or part of their activities, utilities or processes. For example, the diagnosis can focus on the energy consumption of lighting in a network of stores.
In engineering offices, service providers specialized in energy improvement estimate the average duration of an audit at 3 months. The variability remains significant. Beyond the size of the company and the scope selected for the studies, the duration depends on the objectives set and the level of precision expected for the analysis of the dwellings.