1. Price decote formula
The price decote is the average price gap between a property of a given DPE label and an equivalent D-rated property (market reference). Source: French Notaires 2024 green value study (~2.8M transactions analyzed 2018-2023).
prix_attendu = prix_affiche × (1 - decote_pourcentage)
fourchette_basse = prix_affiche × (1 - decote_max)
fourchette_haute = prix_affiche × (1 - decote_min)The decote table is cross-referenced (DPE label × property type: house / apartment / building). Regional variants are applied automatically from the postal code for labels E, F and G: up to 11 calibrated regions (Paris intra-muros -10%, Lyon, Marseille, Aquitaine, rural Nouvelle-Aquitaine -27%, etc.); for apartments, an additional "Paris prime" variant applies (arrondissements 1-8, 16, 17 above €12,000/m², where land scarcity offsets part of the DPE penalty). For building-type properties and (label, region) pairs without a calibrated variant, a national average is applied with a disclaimer.
2. Energy cost projection
Annual energy cost is estimated from the average consumption per label (3CL ADEME method), the living area, the average price of the main energy source, and — for heat pumps — a COP differentiated by type:
cout_annuel = conso_kWh/m²/an × surface × prix_€/kWh / COP
cout_N_ans = Σ_{i=0..N-1} cout_annuel × (1 + inflation)^i- Air / air heat pump: COP 3.0
- Air / water heat pump: COP 3.5
- Geothermal heat pump: COP 4.5
- Default inflation: +3%/year (CRE 2025-2030)
3. Renovation budget & aids
The renovation budget estimates the cost to reach class D from the current label, based on a pre-calibrated typical bundle (roof / wall / window insulation, VMC, heat pump depending on the transition). MaPrimeRénov' aids, CEE and Éco-PTZ are deducted based on the selected income category.
reste_a_charge = cout_total_travaux - aides_mpr - cee
eco_ptz_disponible = min(reste_a_charge, plafond_eco_ptz)4. Regulatory sources
- French Notaires — "Valeur verte" 2024 study (decote table per label × property type × region, ≈ 2.8M transactions 2018-2023)
- BDNB CSTB 2025 — Reference median price per commune (5,524 communes) and IRIS neighborhood (24,681 neighborhoods), for the "market median price" line in results
- CRE — Energy price trajectory 2025-2030 (default inflation +3%/year)
- ADEME — 3CL 2025/2026 coefficients (kWh/m²/year per DPE label, primary energy coefficient electricity 1.9 post-2026)
- ANAH — MaPrimeRénov' 2026 (subsidies by income category Bleu/Jaune/Violet/Rose)
- Climate & Resilience Law (Aug 22, 2021) — Rental ban schedule G (2025) / F (2028) / E (2034)
- Renovation bundles per transition (G→D, F→D, E→D…) — in-house calibration based on ANAH and CSTB feedback
5. Legal compliance (DGCCRF)
The DPE decote calculator applies national statistical averages drawn from the French Notaires "valeur verte" 2024 study (≈ 2.8 million transactions analyzed 2018-2023). The figures are indicative: actual property value depends on specific location, general condition and local market dynamics. In compliance with the DGCCRF, no individual valuation is promised — only a notary or real estate appraiser can value a specific property.
Our approach: (1) all values are presented as "indicative estimates"; (2) low/high ranges are systematically displayed to reflect uncertainty; (3) a disclaimer reminds users that a notary or real estate appraiser remains the sole legally enforceable valuation source; (4) no personal data is collected — calculation is entirely client-side.
6. Known limitations
- Regional variants: applied to labels E, F and G — up to 11 regions (house and apartment), plus a "Paris prime" variant restricted to apartments. Building-type properties and non-calibrated (label, region) pairs fall back to the national average.
- Price/m² estimation: available via CSTB's BDNB 2025 (5,524 communes, including 24,681 IRIS neighborhoods), with a fallback to market data (~1,100 cities). Outside coverage, the "market median price" line is hidden — the percentage decote still applies.
- Energy consumption: middle of the DPE label range (unless actual consumption is entered). For the unbounded G class: 470 kWh/m²/yr (observed G-stock average ≈ 440-500 per Anah).
- Renovation bundle: pre-calibrated per transition (G→D, F→D, etc.). For a custom plan (non-standard combination, condominium), use the dedicated "Renovation Works" tool.