Adresse.ai vs Patrim

Comparing the official French government valuation tool with our buyer-side equivalent. Same underlying data, very different access models.

Updated May 2026.

The short answer

Patrim is the French government’s official property valuation tool, free, accurate, and built directly on the DVF transaction database. Adresse.ai uses the same underlying DVF data, layered with ADEME energy-rating data and our own adjustments. The big difference between the two is access and analysis depth.

This page covers the data foundation that’s shared, the access difference that excludes most pre-purchase buyers from Patrim, the analysis difference that distinguishes the products, and when each tool fits.

Same DVF data, different access path

This is the foundation. Both tools draw on DVF (Demande de Valeurs Foncières), the French government’s mandatory record of every notarised property sale since 2014, published openly via Etalab. The data itself is comprehensive and authoritative; what changes is how the two tools surface it.

Patrim accesses DVF through the impots.gouv.fr tax-account portal. To use it, you need a French numéro fiscal (tax identification number), which is issued to French tax residents and to non-residents who have a specific tax connection to France (notably, owning French property and filing a non-resident return). For most pre-purchase buyers, no numéro fiscal is available; Patrim is effectively a closed door.

Adresse.ai accesses DVF without French government credentials. We pull the open Etalab feeds, layer ADEME energy-rating data and our own adjustments on top, and produce a buyer-side analysis in English. No French tax account required.

For a buyer who has not yet bought a French property, Adresse.ai is the only path to the data analysis between the two. After purchase, when a numéro fiscal becomes available, Patrim is a useful free addition.

What Patrim does

Patrim (sometimes called “Patrim Usagers”) is part of the French Direction Générale des Finances Publiques (DGFiP) infrastructure. The tool:

Lives at impots.gouv.fr, accessible only after logging in to the French tax-account portal.
Returns sale-price information for individual properties and aggregated statistics for areas.
Pulls directly from the same DVF dataset that’s published openly on data.gouv.fr.
Provides search by address or by map.
Shows historical sales, parcel-level details, and area medians.

The strengths:

Authoritative data source: it’s the government’s own portal, with no commercial bias.
Free.
No usage limits.
Useful for ongoing market tracking by existing owners.

The structural limit, for buyers from outside France, is the access requirement. To use Patrim you need:

A French numéro fiscal (tax identification number).
An impots.gouv.fr account.
The ability to navigate a French-language interface.

A non-resident buyer evaluating their first French property typically has none of these.

What Adresse.ai does

Adresse.ai uses the same DVF data Patrim does, plus the ADEME energy-rating data, and adds:

Listing-paste workflow (URL, PDF, or text input).
Per-property adjustments for condition, energy rating, pool, stone character, historic centre, view.
AI qualitative review producing a verdict in plain English.
Confidence band based on comp-pool depth.
Shareable report.

The methodology is fully visible at /how-it-works.

How they compare

Dimension	Patrim	Adresse.ai
Data source	DVF (sale prices) directly	DVF + ADEME + adjustments
Access requirement	French numéro fiscal + impots.gouv.fr login	Standard signup; no French government credentials required
Language	French only	English
Per-property adjustments	None	Yes (visible)
Listing-paste workflow	None	Yes
AI qualitative review	None	Yes
Confidence band	Implicit	Explicit
Best for	Existing French property owners tracking value	Pre-purchase buyers researching French property

Two practical comparisons:

Access. Patrim is a closed door for the typical pre-purchase buyer. The numéro fiscal requirement is structural, not arbitrary; the system is designed for French tax residents to research their own and adjacent properties. An American or British buyer in London evaluating a Provence listing in 2026 has no path into Patrim. Adresse.ai opens the same door from a different side.

Analysis depth. Patrim shows you sale prices. It doesn’t adjust for the things that actually move price (condition, energy rating, pool, stone, view), doesn’t filter intelligently by surface or property type, and doesn’t tell you when the comp pool is too thin to draw a conclusion. You see the data; you don’t see the analysis. For a careful, French-fluent buyer with time on a Saturday afternoon, that’s enough. For a buyer who needs an answer in 45 seconds in English, it isn’t.

When Patrim wins

Two scenarios where Patrim is the right tool:

You already own French property and have a numéro fiscal. Once you’re set up, Patrim is a free way to track local market activity and check what individual properties have sold for. Useful for an annual sanity check of your own property’s value, or for tracking a neighbour’s recent sale.
You’re a French tax resident comfortable in the French interface. The tool was built for this audience and works well for them.

When Adresse.ai wins

Three scenarios where Adresse.ai is the right tool:

You’re a buyer who doesn’t yet own French property. No numéro fiscal, no Patrim. Adresse.ai is the access path.
You want analysis, not just data. Adjustments, comparables on the same property profile, qualitative review. Patrim is the dataset; Adresse.ai is the analysis on top.
You want it in English. Patrim is French-only.

Using both, post-purchase

A common pattern for buyers after they’ve purchased:

Use Adresse.ai during the active deal (the listings, comparisons, and negotiation phase).
After closing and getting your numéro fiscal, set up your impots.gouv.fr account and add Patrim to your toolkit.
For ongoing market tracking, Patrim is the free option; Adresse.ai is the analytical layer when you have a specific question.

A worked comparison

A British buyer is evaluating a stone village house near Uzès, asking €295,000.

Via Patrim, after they own French property and have an account:

Log into impots.gouv.fr, navigate to Patrim.
Search by address.
See the property and 8 to 15 nearby sales over the last 5 years, in French, on a basic map.
Read each sale individually to identify which are genuinely comparable.
Mentally apply adjustments for any property-specific differences they can detect.
Conclude: “Probably in the right range, hard to say more without doing more work.”

Time required: 30 to 60 minutes if French is fluent.

Via Adresse.ai, before they own anything:

Paste the listing.
45 seconds later: a price range of €265,000 to €315,000, midpoint €290,000, comp pool of 19 properties, AI verdict in English, confidence band marked, share link available.

Time required: under a minute.

The two paths produce broadly similar conclusions for the same data, but Adresse.ai does the work that Patrim leaves to the user. For buyers without a French tax account, Adresse.ai is the only tool of the two that’s actually usable.

Questions

Is Patrim more accurate than Adresse.ai?

The underlying data is the same. Adresse.ai layers adjustments and a qualitative review that Patrim doesn’t. Whether that produces a more “accurate” number depends on what you mean: Patrim shows you raw sale prices, Adresse.ai shows you an adjusted estimate calibrated to your specific target. For a buyer evaluating a specific property, the adjusted estimate is more useful. For a researcher looking at the unfiltered market history, Patrim is the right tool.

Why does Patrim require a French tax account?

The system is designed for French tax residents to research their own properties for declaration purposes (notably the IFI wealth tax, which references real-estate values). Opening it to anyone would create privacy concerns around individual sale prices being looked up by adversaries. The numéro fiscal gate is the privacy mechanism.

Could I get a French tax number just to use Patrim?

Possible but bureaucratically painful. The path involves either French tax residency (substantial life change) or a specific tax-related transaction in France (rental income from a French property, for example). Most pre-purchase buyers don’t have an easy route.

Will Patrim ever go fully open?

The raw DVF data is already fully open at data.gouv.fr and at the DVF Etalab map at app.dvf.etalab.gouv.fr. What Patrim adds is an interface tuned for French tax residents; the access gate is structural to its purpose. We don’t expect Patrim itself to open up further, but the underlying data continues to improve in coverage and timeliness.

Is the DVF Etalab map a free alternative to Patrim?

Partly. The Etalab map at app.dvf.etalab.gouv.fr is fully open (no login required) and shows individual sale records on a map. It’s harder to use than Patrim but covers the same data. For a buyer who wants a free-only path with no tools layered on, it’s the option. The trade-off is that you’re doing all the analysis yourself, in French, against raw data.

Try it on your listing

If you don’t have a French numéro fiscal yet, Adresse.ai is the buyer-side path.

Run an estimate →