How utilities bill stormwater accounts quarterly by impervious surface area: ERU calculation, parcel data, accounts with no water service, and setup steps.
For US Utilities serving 3,000-100,000 meters and for operations team, billing team and utility managers. For Heads of Billing who own collections accuracy and revenue leakage.
Stormwater accounts billed quarterly by impervious surface area are charged a fee based on how much hard surface on each parcel, such as roofs, driveways, and parking lots, sends runoff into the storm system, billed once every three months. Most utilities convert each parcel's impervious area into equivalent residential units (ERUs) and charge a set rate per ERU, usually on the same bill as water and sewer. A water utility management platform bills it as a non-metered charge on its own billing frequency. This guide covers how the fee is calculated, where the data comes from, and how to set up quarterly billing.
Does your stormwater fee follow the runoff each parcel creates, or charge every property the same?
Stormwater has no meter, so the fee needs a stand-in for how much runoff each property sends to the system. Impervious surface area is the most common stand-in, because hard surfaces shed rain instead of absorbing it. Utilities use one of a few methods to turn that area into a charge.
The ERU method is the most widely used because it is fair across property types and simple to explain. A worked example, using round illustrative numbers rather than any specific utility's rates, shows how it reaches a quarterly bill:
Your own ERU size, rounding rules, and rate come from your rate study and ordinance. The billing system's job is to apply them consistently to every account, every quarter. How stormwater fees sit alongside water, sewer, and other charges on a combined bill is covered in the overview of software used for billing at water utilities.
The billing system does not measure impervious area. It receives a number for each parcel from another source and bills against it. Common sources include:
The weak point is keeping this data current. A new parking lot that never reaches the billing record is lost revenue, and a demolished building that stays on the record is an overcharge and a likely appeal. Most utilities refresh impervious area on a set schedule, such as each year, and update individual parcels when permits close. The same GIS records also support the storm system itself, covered in the guide to stormwater asset and work order management.
Stormwater fees can be billed monthly, quarterly, or once a year. Quarterly is common because the charge does not change with usage, so a monthly bill adds work without adding information.
A common setup is a stormwater charge that follows each account's existing billing frequency, plus quarterly standalone bills for parcels that have no water account.
Who receives the stormwater bill for a parking lot with no water meter?
The hardest stormwater accounts are the parcels that create runoff but have no water or sewer service: parking lots, vacant commercial land, and some churches, schools, and storage yards. They need their own account and their own bill. To handle them, a billing system needs to:
These accounts are similar to other non-standard accounts that need their own setup, such as park and irrigation services, covered in the guide to parks and irrigation water billing.
Because the fee depends on a measurement the customer did not make, every stormwater program needs a fair way to change it. A billing system should support:
Each change should leave an audit trail showing who changed the parcel's ERUs or credit, when, and why. Without it, appeals and rate reviews turn into a search through email and paper files.
Is every parcel that creates runoff linked to a billing account today?
Work through the setup in this order:
The step utilities most often underestimate is step 3. Matching parcels to accounts takes longer than expected, especially where one owner holds many parcels or a parcel has several water services.
Stormwater billing looks simple because there is no meter, but it puts specific demands on the billing system.
SMART360 bills stormwater as a non-metered service alongside water, sewer, and waste charges on one platform.
SMART360 serves utilities with 3,000 to 100,000 connections at per-connection pricing, with implementation in 20 to 24 weeks.
The utility measures the hard surface on each parcel, such as roofs and pavement, and converts it into equivalent residential units (ERUs), where one ERU is the impervious area of a typical home. Each account is billed a set rate per ERU. Homes usually pay for one ERU, and larger commercial parcels pay for many.
An ERU is a billing unit equal to the impervious area of a typical single-family home in the utility's service area. The utility sets the ERU size in its rate study. A parcel's ERU count is its impervious area divided by the ERU size, usually rounded under rules set in the ordinance.
Stormwater charges do not change with usage, so a monthly bill adds work without adding information. Quarterly billing fits utilities that already bill water and sewer quarterly and keeps the number of standalone bills down for parcels that have no water account, such as parking lots and vacant land.
Create a stormwater-only account from the parcel and ownership records, bill the property owner at their mailing address, and send a standalone bill on the stormwater billing frequency. Where the ordinance allows, combine parcels with the same owner onto one bill. These accounts should follow the same collections process as other accounts.
Yes. SMART360 bills stormwater as a non-metered service with fixed charges, using billing plans that set the frequency for each service, so stormwater can bill quarterly while water bills monthly. Customer categories apply different charges to residential and non-residential accounts, and stormwater appears on the same bill as water, sewer, and waste.
Stormwater accounts billed quarterly by impervious surface area work when the parcel data is current, every parcel that creates runoff has an account, and credits and appeals are traceable. Adopt the rate structure, build the parcel dataset, match parcels to accounts, configure stormwater as a non-metered quarterly charge, and test a full cycle before the first live bill. How stormwater fits into the rest of a water utility's billing is covered in the guide to water utility billing software. To see how SMART360 bills stormwater with water and sewer on one platform, book a demo.
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