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Good practice Imported

Poznań's Retention-Linked Stormwater Fee — Aquanet's Avoided-Cost Discount Scheme (Poland)

Poland · Poznań · See the Poland profile · See the Poznań profile

Evidence: Descriptive / self-reported Top 84% 33/100 · Ask Evidence Copilot about this practice

Poznań's water utility Aquanet discounts stormwater fees by roughly 15% for properties that retain over 20% of rainfall on-site, pairing the price signal with municipal grants for rain gardens and retention tanks.

~15%
Stormwater fee discount for retaining over 20% of rainfall on-site (effective Aug 2025)
>20% of rainfall/snowmelt retained on-site
Retention threshold to qualify for the discount
Poznań's Retention-Linked Stormwater Fee — Aquanet's Avoided-Cost Discount Scheme (Poland)

Details

Maturity
Established
Promoter
Aquanet S.A. / City of Poznań
Period
2021–present
Region (NUTS)
PL41
Keywords
water utility, stormwater fee, green infrastructure, municipal governance

Context

Since around 2021, Poznań's municipal water and sewage utility Aquanet has priced stormwater discharge on a sliding scale: properties with no on-site retention pay the standard rate, while those retaining more than 20% of rainfall and snowmelt on-site qualify for a discount. Aquanet's tariff, effective August 2025, sets combined-sewer discharge at 8.06 PLN/m³ falling to 6.84 PLN/m³, and separate storm-sewer discharge at 7.77 PLN/m³ falling to 6.60 PLN/m³ — a roughly 15% saving for maximal retention. A complementary municipal 'small retention' grant programme covers up to 80% of retention-device costs (up to 50,000 PLN for housing cooperatives, 6,000 PLN for individual households) from a 1 million PLN annual budget.

Implementation
Indicative cost
Low (< €50k) — Municipal small-retention grant budget: 1,000,000 PLN/year, covering up to 80% of device costs (capped at 50,000 PLN for housing cooperatives, 6,000 PLN for individual households).
Time to results
Long (> 3 years) — Discount tariff operating since around 2021; current rates effective August 2025.
Staffing & skills
Aquanet S.A. (water utility, administers the tariff), City of Poznań (co-runs the small-retention grant programme)

Conditions for success

  • Property owners installing qualifying on-site retention devices (rain gardens, retention tanks) to reach the >20% retention threshold
  • Sustained municipal grant budget to offset installation costs and encourage uptake
  • Public acceptance of stormwater charges — a peer-reviewed comparison notes Warsaw and Kraków have not adopted equivalent fees, citing public resistance

Common failure modes

  • No published data exists on total impervious area affected or aggregate retention volume achieved city-wide, so measured effectiveness is unverified
  • Public resistance to new stormwater charges has stopped larger Polish cities (Warsaw, Kraków) from adopting equivalent schemes

Commonly funded by

Own resources / municipal budget

Indicative funding routes for practices of this type — always check each programme's current calls and eligibility rules.

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Data sources

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