Key takeaway: A single-family home on county water and sewer that uses 6,000 gallons a month pays roughly $118 to $165 a month for the two combined in late 2026: about $165 on Oʻahu, $148 on Kauaʻi, $135 on Maui and $118 on Hawaiʻi Island. These are our calculations from each county’s published rate schedules (sources in each county section below). Sewer is the bigger half of the bill everywhere except Hawaiʻi Island. Many neighbor-island homes aren’t on a sewer at all and pay for a cesspool or septic system instead. Last checked November 2026.
Water and sewer are billed by the county, not by a private utility, so the rates are set by each county’s water board or council and change on a published schedule. Several counties are in the middle of multi-year increases, and all four counties changed water or sewer rates in 2026. If you’re comparing rentals, ask whether water and sewer are included. In condos they usually are, through the maintenance fee.
How much is a water and sewer bill in each county?
| Monthly, single-family home, 6,000 gallons | Oʻahu (Honolulu) | Maui County | Kauaʻi | Hawaiʻi Island |
|---|---|---|---|---|
| Water bill | $57.18 | $45.88 | $57.24 + power adjustment | $66.24 |
| Sewer bill | $107.42 | $89.50 | $91.00 | $52.00 |
| Total | about $165 | about $135 | about $148 | about $118 |
| Water rates in effect since | July 1, 2026 | July 1, 2026 (FY2027) | Nov 1, 2026 | July 1, 2026; power charge Oct 1, 2026 |
| Sewer rates in effect since | July 1, 2026 | July 1, 2026 (FY2027) | July 1, 2026 (FY2027) | April 1, 2023 |
Our calculations for a 5/8-inch residential meter, from the rate schedules cited in each county section below. Maui sewer uses the county’s FY2027 rate schedule; Kauaʻi’s water bill excludes a cost-of-power adjustment we couldn’t find a current amount for. Totals are rounded.
Oʻahu: Board of Water Supply and city sewer charges
The Honolulu Board of Water Supply charges a single-family home $17.30 a month for a standard 5/8- or 3/4-inch meter from July 1, 2026, plus a tiered charge per 1,000 gallons: $4.92 for the first 2,000 gallons, $7.51 from 2,001 to 6,000, $8.98 from 6,001 to 30,000 and $15.06 above that (BWS rate schedule FY2024–FY2029). Increases are already adopted for each July through 2028. In July 2027 the monthly charge goes to $18.68.
Sewer is the larger part of an Oʻahu bill. The city restructured its sewer fee in 2026, lowering the fixed base charge and raising the usage charge. From July 1, 2026, a single-family home on city water pays a $48.27 monthly base plus $11.83 per 1,000 gallons. Billed volume is 80% of the water you use, an automatic 20% discount for homes without a separate irrigation meter, for water that doesn’t go down the drain. Homes not on city water pay a flat $133.42 (Honolulu Dept. of Environmental Services). The schedule rises every July through 2031, to $52.37 plus $12.83 in July 2027.
Worked example, 6,000 gallons: water is $17.30 + 2 × $4.92 + 4 × $7.51 = $57.18. Sewer is $48.27 + 5 × $11.83 = $107.42 (80% of 6,000 gallons is 4,800, which the city’s own sample bills round to 5,000). Total: about $165. A household that uses less water saves more on Oʻahu than anywhere else, because most of the sewer bill now follows usage.
Maui County: Department of Water Supply and wastewater
For fiscal year 2027 (July 1, 2026 to June 30, 2027), Maui’s Department of Water Supply charges $30.25 a month for a 5/8-inch meter, plus $2.13 per 1,000 gallons for the first 5,000 gallons, $4.98 from 5,001 to 15,000, $9.59 from 15,001 to 35,000, and more above that (Maui DWS FY2027 rates and fees). During a declared drought, the upper tiers go up.
The county’s FY2027 rate schedule sets single-family sewer at a $61.00 monthly base plus $4.75 per 1,000 gallons, charged on the first 9,000 gallons only, so the most a home pays is $103.75. Homes not on county water pay a flat $75.50 (Maui County FY2027 budget, Appendix B). The county’s residential fees page still lists the previous year’s rate of $51.00 plus $4.60 (Maui County).
Worked example, 6,000 gallons: water is $30.25 + 5 × $2.13 + 1 × $4.98 = $45.88. Sewer is $61.00 + 6 × $4.75 = $89.50. Total: about $135.
Kauaʻi: new water rates from November 2026
Kauaʻi’s Department of Water adopted new rates in September 2026, effective November 1, 2026. The monthly service charge for a 5/8-inch meter is $22.19, and use charges are $4.75 for the first 1,000 gallons, $6.06 per 1,000 from 1,000 to 7,000 gallons, $7.06 from 7,000 to 14,000 and $11.88 to $12.50 above that (Kauaʻi DOW rate rules, rev. Sept 24, 2026; DOW announcement). Further steps are adopted every July through 2030. In July 2027 the service charge rises to $27.73. A cost-of-power adjustment is also charged per 1,000 gallons; we couldn’t find the current amount on the department’s site.
Kauaʻi sewer is a flat monthly charge with no usage component: $91.00 for a single-family home in FY2027, rising to $101.00 in FY2028 (Kauaʻi County Code, Ch. 25).
Worked example, 6,000 gallons: water is $22.19 + $4.75 + 5 × $6.06 = $57.24, plus the power adjustment. Sewer is $91.00. Total: about $148. About 54% of Kauaʻi households use cesspools rather than a sewer (Hawaiʻi DOH Cesspool Conversion Working Group, 2023), so many homes pay only the water bill.
Hawaiʻi Island: water plus a power cost charge
Hawaiʻi County’s Department of Water Supply charges a monthly standby charge of $35.93 for a 5/8-inch meter from July 1, 2026. Usage is $1.64 per 1,000 gallons for the first 5,000, $3.57 from 5,001 to 15,000, $6.28 from 15,001 to 40,000 and $8.34 above that. On top of usage comes a power cost charge, recalculated every two months, which was $3.04 per 1,000 gallons from October 1, 2026, plus a small energy charge, last listed at $0.05 per 1,000 (Hawaiʻi DWS water rates). In our example, the power charge is larger than the usage charge itself.
County sewer is a flat $52.00 a month per residential unit, unchanged since April 2023 (Hawaiʻi County Ordinance 2019-21). A proposed increase to $63 in January 2027, rising in steps to $125 by 2031, was deferred by a County Council committee in September 2026 and had not been adopted as of our last check (Big Island Now, Sep 2026). Most of the island isn’t on a sewer: a 2023 Department of Health working-group briefing says 71% of the county is without sewers (DOH briefing), and the county has nearly 50,000 cesspools (Hawaiʻi DOH).
Worked example, 6,000 gallons: water is $35.93 + 5 × $1.64 + 1 × $3.57 + 6 × $3.04 power + 6 × $0.05 energy = $66.24. Sewer is $52.00. Total: about $118.
What if the home has a cesspool or septic system?
Hawaiʻi has about 88,000 cesspools: nearly 50,000 on Hawaiʻi Island, almost 14,000 on Kauaʻi, over 12,000 in Maui County and over 11,000 on Oʻahu. Act 125 of 2017 requires all of them to be replaced by 2050 (Hawaiʻi DOH). A home on a cesspool has no sewer bill, but a buyer should budget for the conversion to a septic system or a sewer connection before then. When you’re buying, ask what the home uses and check our home buying costs guide.
Frequently asked questions
How much is the average water bill in Honolulu?
For a single-family home using 6,000 gallons a month, the Board of Water Supply bill is about $57 at rates effective July 1, 2026, and the city sewer charge adds about $107, for roughly $165 combined (our calculation from BWS and Honolulu ENV rate schedules).
Which Hawaiʻi county has the cheapest water and sewer?
Hawaiʻi County, at about $118 a month for 6,000 gallons on county water and sewer, mainly because its sewer charge is a flat $52. Its water bill alone is the highest of the four, about $66, because of its power cost charge. Oʻahu is the most expensive combined, at about $165.
Why are Oʻahu sewer bills so high?
Honolulu is paying for upgrades required by a 2010 federal consent decree, including a secondary-treatment upgrade at the Sand Island plant, and its rate schedule rises every July through 2031. From July 1, 2026 the charge is $48.27 a month plus $11.83 per 1,000 gallons, billed on 80% of water use (Honolulu Dept. of Environmental Services).
Are water and sewer rates going up in Hawaiʻi?
Yes, on most islands. Oʻahu water rates are adopted through July 2028 and sewer through July 2031; Kauaʻi water rises every July through 2030 and sewer to $101 in FY2028. Hawaiʻi County’s proposed sewer increase was deferred in committee in September 2026.
Do I have to replace a cesspool in Hawaiʻi?
Yes, by 2050. Act 125 of 2017 requires every cesspool in the state to be replaced (Hawaiʻi DOH).
Related guides
- Electricity rates by island: why your bill depends on where you live
- Move-in costs in Hawaiʻi: deposits, GET and what to have saved
- Utility deposits and connection fees in Hawaiʻi by island, including county water deposits
- Buying a home in Hawaiʻi: prices by island, closing costs and condo fees
- Property tax in Hawaiʻi: rates by county for 2026–27
- Compare the islands: cost of living side by side
Sources
- Honolulu Board of Water Supply: rate schedule FY2024–FY2029
- Honolulu Dept. of Environmental Services: sewer fee rates
- Maui County Dept. of Water Supply: FY2027 rates and fees
- Maui County FY2027 budget, Appendix B: rates and fees
- Maui County: residential sewer fees
- Kauaʻi Dept. of Water: rate rules, rev. Sept 24, 2026
- Kauaʻi Dept. of Water: rate increases effective Nov 1, 2026
- Kauaʻi County Code, Ch. 25: sewer charges
- Hawaiʻi County Dept. of Water Supply: water rates
- Hawaiʻi County Ordinance 2019-21: sewer rates
- Big Island Now: sewer rate bill deferred, Sep 2026
- Hawaiʻi Dept. of Health: cesspools
- Hawaiʻi DOH Cesspool Conversion Working Group briefing, 2023