The Eco-social water tariff in Dunkerque, France

Climate change threatens water availability, requiring efficiency gains, but higher prices risk denying low-income households the human right to safe drinking water. Dunkerque's water utility, the Syndicat de l'Eau de Dunkerque (SED), serves around 215,000 inhabitants; drinking water comes from groundwater over 40 km away (Audomarois) while surface water serves the area's intense industry, via two separate networks built in the 1970s. The former Nord-Pas de Calais region has one of France's highest poverty/social-exclusion rates (25.9% in 2022).

As one of 50 local authorities in a national experimentation, Dunkerque introduced an eco-social tariff -- a metered, tiered water-pricing system aiming to (1) decrease water consumption and resource use, (2) raise environmental awareness via financial incentives, and (3) introduce automatic social discounts for low-income households, removing bureaucratic access barriers by using CSS/CPAM (health-insurance) eligibility data.

A three-tier pricing structure distinguishes essential from non-essential use: tier 1 (up to 80 m3/year per household) priced at 1.29 EUR/m3 (subsidised), tier 2 (up to 200 m3) at 2.40 EUR/m3, tier 3 (above 200 m3) at 3.18 EUR/m3 (all 2023 prices); CSS beneficiaries get an automatic 70% discount, paying 0.50 EUR/m3. In 2023, 72.1% of households stayed within tier 1, 25.4% reached tier 2, and 2.6% reached tier 3. Because the tariff cannot account for household size directly, about 1,600 households in collective buildings without individual meters (out of 36,000 area multi-family dwellings) and larger households could not benefit automatically; a 'Cheque eau' (12 EUR/year per person from the sixth household member; 40 EUR/year for un-metered collective housing) was introduced but drew only about 40 of over 1,800 expected applicant households, so SED is seeking data-sharing with the CAF (family allowance fund) to automate this as it already does with CSS data.

A 2017 report (most recent cost data) put establishment costs at about 180,000 EUR (tariff design consultancy, meter installation, implementation planning), plus an ongoing 1.5 cents/m3 billing-system management cost. 80% of consumers saw bills fall or stay level; the remaining 20% (mostly tier-3 high consumers) saw increases. Average household consumption fell from 83-85 m3/year (2010) to 67 m3/year (2023); tier-2 consumption fell from about 90 m3/year (2010) to under 80 m3/year (2013). Groundwater abstraction fell by 10% in 2023, and SED saved 10% in costs versus the previous tariff. Tier-1 consumption rose slightly (from below 70 to over 75 m3/year), suggesting prior under-consumption by budget-constrained households, now able to meet basic needs more fully; one household in two fell below the previous system's break-even threshold.

The tariff is judged effective both environmentally and socially, redistributing costs so 80% pay the same or less while reducing overall consumption and letting previously under-consuming low-income households modestly increase use. A major awareness campaign launched before the tariff, and continuing in 2024 through cultural, sporting and school events, is credited with the programme's acceptance, aiming to inform users about water's origin/value, the tariff's rationale, and practical conservation habits. Persistent limitations include un-metered collective housing (16,000 households), inability to fairly account for large-household water needs (partly blocked by a data-sharing refusal from the relevant subsidy body, though a national regulatory decree is expected to mandate such sharing), and the failed opt-in cheque system, which has been abandoned. The first-tier threshold was raised from 75 to 80 m3/year in 2018 to cover more households. Post-COVID digitalised payment has been linked to rising unpaid bills, particularly among elderly and less digitally literate residents.