In short: under a tiered (block) rate, only the usage inside each block is billed at that block's price — the rate does not apply retroactively to your whole bill. For 6 CCF (about 4,488 gallons) on the default three-tier schedule shown above, that comes to $35.70: $23.20 of tiered usage charges plus a $12.50 fixed service charge.
This is a planning estimate. Enter the exact tiers, rates and fixed charge from your own water bill or your utility's published rate schedule for an accurate figure.
How a tiered water bill is calculated
A tiered or block rate splits your usage into consecutive bands, each with its own price per unit. The first band is billed at the lowest rate; once your usage crosses into the next band, only the usage inside that band is billed at the higher rate — the earlier, cheaper units stay at the earlier price. The calculator works through the tiers in order, filling each one before moving to the next:
tier charge = Σ (usage in block × block rate), for each tier
total bill = tier charges + fixed service charge + sewer charge (if included)
Only usage that falls inside a given tier's range is billed at that tier's rate; usage below the tier's lower boundary was already billed in earlier tiers, and usage above its upper boundary carries forward to the next tier.
Worked example. On the default schedule — Tier 1 up to 4 CCF at $3.25, Tier 2 from 4–10 CCF at $5.10, Tier 3 above 10 CCF at $7.85 — a household using 6 CCF pays the Tier 1 rate on the first 4 CCF (4 × $3.25 = $13.00) and the Tier 2 rate on the remaining 2 CCF (2 × $5.10 = $10.20), for $23.20 in usage charges. Add the $12.50 fixed service charge and the total comes to $35.70.
Example tier schedule used above
This is the illustrative default the calculator loads with — not a real utility's published rate. Replace it with your own utility's tiers before relying on the total.
| Tier | Usage range | Rate | Cost at 6 CCF usage |
|---|---|---|---|
| Tier 1 | 0–4 CCF | $3.25 / CCF | $13.00 |
| Tier 2 | 4–10 CCF | $5.10 / CCF | $10.20 |
| Tier 3 | Above 10 CCF | $7.85 / CCF | $0.00 |
| Fixed charge | — | — | $12.50 |
| Total | 6 CCF used | — | $35.70 |
Worked scenarios
Three households on the same default schedule, to show how quickly tiers can move the total.
Low usage — 3 CCF
$22.25
All 3 CCF stays in Tier 1: 3 × $3.25 = $9.75, plus the $12.50 fixed charge.
Default usage — 6 CCF
$35.70
4 CCF in Tier 1 ($13.00) plus 2 CCF in Tier 2 ($10.20), plus the $12.50 fixed charge.
High usage — 15 CCF
$95.35
4 CCF in Tier 1 ($13.00), 6 CCF in Tier 2 ($30.60), 5 CCF in Tier 3 ($39.25), plus the $12.50 fixed charge.
With sewer included at $4.75/CCF, the 8 CCF case runs $33.40 in tiered water charges (4 CCF at $3.25 + 4 CCF at $5.10) plus $38.00 sewer plus $12.50 fixed — $83.90 total. Toggle the sewer charge on above to see this reflected live.
What else affects your real bill
Seasonal and drought rates. Some utilities raise tier rates or shrink tier widths in summer, or add a drought surcharge during restrictions. Use the rates in effect for the billing period you're checking, not an annual average.
Minimum bills and included allowances. Some fixed charges already include a small usage allowance (for example, the first 2 CCF free), which changes where Tier 1 effectively starts. Check your rate schedule for this before entering tiers.
Sewer caps. Many utilities cap sewer charges at a customer's average winter water usage, since summer irrigation shouldn't inflate the sewer bill. If that applies to you, enter the capped figure as your usage for the sewer calculation rather than your full metered usage.
To estimate the usage figure itself before you have a bill in hand, try the household water usage calculator.
Frequently asked questions
What is a tiered (block) water rate?
A tiered or block rate charges a different price per unit of water depending on how much you use. The first block of usage is billed at the lowest rate, the next block at a higher rate, and so on. Only the usage that falls inside each block is billed at that block's rate — not your entire usage.
How do I find my utility's tier breakpoints and rates?
Your water bill or your utility's published rate schedule (often called a tariff or rate ordinance, usually posted on the utility's website) lists the tier breakpoints and the price per unit for each tier, plus any fixed monthly service charge. Enter those exact figures into the calculator.
Does this calculator include sewer charges?
There is an optional sewer charge you can turn on, calculated as your water usage multiplied by a per-unit sewer rate. Many utilities bill sewer this way, though some cap it at a winter-average usage figure instead — check your bill and adjust the usage figure if that applies to you.
Why does my bill go up faster than my usage?
Because higher tiers charge more per unit, each additional unit of water in a higher tier costs more than the last. A household that doubles its usage from the first tier into the third tier will often see its bill more than double, since the extra usage is billed at the top rates.
What if my utility bills in gallons instead of CCF?
Change the usage unit to gallons (or 1,000 gallons, or cubic meters) and enter your tier breakpoints and rates in that same unit, exactly as they appear on your bill. The calculator does not convert tier numbers between units for you, since utilities define their own blocks.
Is the fixed service charge part of the total?
Yes. The fixed monthly service charge (sometimes called a base charge or meter charge) is added to the usage-based tier charges and any sewer charge to produce the total bill shown in the result panel.
Sources & references
- American Water Works Association (AWWA). Manual M1: Principles of Water Rates, Fees, and Charges.
- U.S. Environmental Protection Agency (EPA). Water Finance Clearinghouse — rate-setting resources.
- Your water utility's published rate schedule is the authoritative source for the actual tiers, rates, and fixed charges that apply to your account.
Sarah Bennett, MS
Water Quality & Sustainability Specialist · Portland, Oregon
Environmental scientist (MS, Water Resources) with 9+ years in residential water quality, treatment, and usage efficiency, and 150+ completed assessments. Sarah writes and reviews the treatment, usage, and cost calculators on watercalculator.us. Read full bio
MS Environmental Science, Water Resources (2018) · BS Environmental Engineering (2016)