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Daily demand → usable storage → days of autonomy → refill plan

Off-Grid Water Autonomy Calculator

Build a household water budget from real activities, calculate how long a tank lasts above your reserve, compare conservation and emergency scenarios, and plan refills from a well, rainwater system or delivered water.

Demand by activityShowers, toilets, laundry, dishes, faucets, outdoor use and custom needs.
Tank autonomySeparate current water from the reserve you do not plan to consume.
Scenario comparisonCompare normal, conservation and emergency demand without creating separate pages.
Refill feasibilityCompare entered source flow, available hours, household use and pump energy.
1,000-gallon planning example: a tank at 70% contains 700 gallons. Holding 20% as reserve leaves 500 usable gallons. At 100 gallons/day with 20 gallons/day of reliable inflow, the entered system reaches reserve in about 6.25 days.

Build a daily water budget

Use measured fixture flow and actual household habits where possible. National averages are context, not a design requirement for your cabin or off-grid system.

Daily water budget

Total daily use—
Weekly use—
Monthly use—
Liters/day—
CategoryGallons/dayShare

Copy or print the current plan

Use a calculator mode above to generate a planning summary.

Start with measured household demand

EPA says the average American uses about 82 gallons per day at home, while the average family uses more than 300 gallons per day and roughly 70% is indoors. Those figures provide context, but an off-grid design should use your actual fixtures, routines, outdoor demand and seasonal conditions.

daily demand = showers + toilets + laundry + dishes + faucets + drinking/cooking + outdoor/custom use

Track tank level or meter readings over several representative days. Separate normal, conservation and emergency scenarios rather than relying on one optimistic estimate.

Reserve, source reliability and water quality

A reserve floor prevents the calculator from treating every gallon in a tank as normally available. The refill model only compares entered flow, hours and demand; it does not verify aquifer recovery, pump curves, treatment or potable quality.

Private well owners are responsible for the safety of their drinking water. EPA notes that private wells are generally not regulated under the federal Safe Drinking Water Act, and CDC recommends at least annual testing for total coliforms, nitrates, total dissolved solids and pH using appropriate local guidance and certified laboratories.