Final/primary energy coefficient: guide for tradespeople (2026)

Understanding the difference between final energy and primary energy

Final energy: what the client consumes and what you bill (kWh at the meter)

Final energy is what your client sees passing through their meter. Gas in kWh, electricity in kWh, fuel oil in converted liters, wood in stères or kg. It is also the basis of the bill. For you, it is the most concrete benchmark for estimating consumption after work and explaining the savings, at the meter.

Primary energy: the energy "before delivery" and its production/transport losses

Primary energy corresponds to the energy mobilized at the source to supply the final energy. It includes losses linked to production, transformation and transport. This is particularly visible for electricity. Part of the energy is "lost" before reaching the client. This is referred to as a level before delivery.

Why this coefficient exists: comparing uses (electricity, gas, wood) on a common basis

The coefficient puts all uses on the same calculation rule. Otherwise, you would be comparing "kWh" that do not carry the same upstream energy cost. In energy balances and the DPE, primary energy is used to classify a home on a common basis, regardless of the energy carrier.

Conversion coefficient: how to go from final energy to primary energy

The simple formula to use on site: primary energy = final energy × coefficient

On a quote or an energy balance, you often start from final energy (the figure measured at the meter or on the bill). To compare solutions and align with DPE methods, a coefficient is applied. Common example: 1 kWh of electricity consumed becomes 2.3 kWh of primary energy. For gas, fuel oil or wood, the factor is often close to 1, but it can vary depending on the network.

Where to find the right coefficient: DPE, energy audit, technical data sheets and official texts

The simplest approach is to use the coefficient stated in the DPE report or in the energy audit. You also find it in certain technical data sheets (particularly for district heating networks) and, above all, in the texts governing the DPE and energy regulations. If in doubt, rely on the project's binding document, not on a value taken "by feel".

Common conversion mistakes: units, reference periods and rounding

• Mixing kWh/year and kWh/m².year. Convert first, normalize afterward.
• Comparing different periods (month, year, heating season). Keep the same basis.
• Rounding too early. Keep 2 decimal places until the total, especially if the energy difference is small.

What this changes in energy renovation: DPE, audit and choice of work

Impact on the home's energy class: why electricity "weighs" differently

The DPE does not just look at your billed kWh. It converts to primary energy. Electricity is therefore multiplied by a coefficient different from gas or wood. As a result, two homes with the same bill can display a different energy class. In 2026, the energy audit complements this diagnosis to prioritize the measures that truly raise the label.

Concrete cases: insulation + ventilation, heating, domestic hot water

• Insulation and airtightness first, otherwise you are heating the outdoors. Then suitable ventilation to keep the air healthy.
• Heating next, sized after the work. A better-insulated house allows a smaller, more efficient heat generator.
• Domestic hot water, often overlooked. A heat pump water heater, solar, or simple adjustments can reduce consumption year-round.

Heat pump, boiler, stove: comparing correctly thanks to the conversion

To choose, compare on the same basis. The DPE expresses figures in kWh of primary energy, but your cost of use also depends on billed kWh, efficiency and the actual need after insulation. A heat pump can perform very well if the house is consistent and well ventilated. A wood stove can help as a supplement. A boiler remains relevant if the network and usage patterns suit it.

Subsidies and obligations: talking about "energy" correctly in your files in 2026

MaPrimeRénov' and CEE: when primary/final energy comes into play in supporting documents

In MaPrimeRénov', performance elements are often based on the DPE or the audit, expressed in primary energy. On manufacturer data sheets and invoices, you instead find values in final energy. To avoid back-and-forth, clearly state the unit, the scope (home, system, measure) and keep kWh figures consistent from one document to another.

RGE and inspections: securing your documents (quotes, product sheets, certificates)

In 2026, the strength of a file rests on simple but rigorous documents. A dated quote, SIRET number, RGE mention at the right point, precise description of the work, verifiable characteristics (e.g. R-value for insulation, ETAS for a heat pump), and product references. Organize everything from the start, like a well-labeled electrical panel. Goal: clean evidence.

Condominiums and single-family homes: points of attention on reference consumption

In a house, the reference is often the home's own DPE. In a condominium, there can be a collective DPE, an audit, and consumption figures that mix private and shared areas. Specify the situation (collective heating or not), the surface area used, and the reference period. A clear reference avoids "losing" energy in paperwork.

Field method: explaining the coefficient to the client and avoiding disputes

Two-minute explanation: a simple comparison to get the message across

Explain the coefficient like an exchange rate. You start from a real figure (bill, kWh, liters of fuel oil) and "translate" it into another unit everyone understands. In renovation, this is often used between final energy and primary energy. The client remembers a simple idea. Same use, two ways of counting it.

Quoting before/after: presenting energy savings without promising the impossible

Present a before/after with a range, not a figure set in stone. Base it on 12 months of consumption, then adjust to a comparable climate (heating degree days) and consistent usage. Announce an order of magnitude in kWh and euros, while noting that weather and habits can change.

End-of-visit checklist: data to collect for a reliable conversion (2026)

• Energy sources and contracts (electricity, gas, fuel oil, wood). Meter reading and 12 months of bills.
• Actually heated surface, ceiling height, unheated zones.
• Generator (make, power, age), emitters, control system, setpoint.
• Ventilation, perceived airtightness, existing insulation.
• Assumptions noted in writing. Conversion coefficient used (2026 reference).