The baseline rate
$0.0115 per gallon, combined water and sewer. US average combined water + sewer, ~$11.50 per 1,000 gallons. Varies 3x by utility; override with your own bill. Checked 2026-08-31.
This one matters more than it looks, because sewer is billed on metered intake rather than on what reaches the sewer. Every gallon a reverse osmosis system rejects is therefore charged twice. Rates vary roughly threefold between utilities, so the calculator lets you put your own in — take it off your bill.
Per option
| Option | Upfront | Consumables/yr | Per gallon | Waste ratio | Fees/mo |
|---|---|---|---|---|---|
| Tap water, unfiltered | — | — | $0.011 | — | — |
| Filter pitcher | $28.33 | $63.00 | $0.011 | — | — |
| Countertop reverse osmosis | $389 | $70.00 | $0.011 | 2:1 | — |
| Under-sink reverse osmosis | $235 | $85.00 | $0.011 | 3:1 | — |
| Self-serve refill station | $30.00 | — | $0.420 | — | — |
| Bulk bottled water | — | — | $1.140 | — | — |
| Home delivery service | — | — | $1.700 | — | $12.00 |
Consumables are quoted at two gallons a day and scale with volume, with a floor — a filter has a shelf life whether or not you use it.
What this model deliberately leaves out
- Your time, priced. The table shows lifting and effort as their own column rather than converting them to dollars, because an hourly rate for your own Saturday is a fiction. A hundred and twenty minutes a month of hauling jugs is a real cost; it is just not a dollar one.
- Water quality. This model prices supply, not treatment outcomes. If your utility report shows a contaminant near a limit, the cheapest option is not automatically the right one, and no calculator should tell you otherwise.
- Resale, disposal and plastic. Real considerations, not costs I can source honestly, so they are absent rather than guessed.
Corrections
If a figure here is out of date or wrong, it should be corrected in public rather than quietly. When one changes, the change and its date go on this page — a site whose argument is arithmetic has no business hiding its revisions.