Worked household examples
Explore 84 worked examples grouped by tool. Each uses fictional data and shows the inputs, arithmetic and a comparison you can adapt to your own household.
Electricity & Water Bill Calculator
- Four-person tiered water bill
- Rebuild a flat-rate electricity statement
- Split a two-person apartment electricity bill
- Read a four-person flat-rate water bill
- Recalculate service charges and tax
- Combine water and sewer unit charges
- Find the break-even usage for two plans
- Price extra use across an electricity tier
- Convert a US gallon meter for a CCF tariff
- Compare bills with different billing days
Appliance Energy Cost Calculator
- One-person home office
- Air conditioning during an eight-hour window
- Use an average reading for a cycling refrigerator
- Estimate the cost of a bank of LED lights
- Compare television picture modes
- Turn a washer cycle reading into a monthly cost
- Compare drying time after a faster spin
- Count oven preheat energy separately
- Estimate a humid week in the basement
- Price a router and idle network accessory
Utility Bill Detective
- Explain a bill with higher use and a higher rate
- Isolate an electricity usage increase
- Check a rate change with stable consumption
- Find a fixed-fee increase in the bill lines
- Investigate the residual from a higher electricity block
- Check whether daily electricity use really rose
- Separate a summer usage spike from a price change
- Check a water spike against the meter
- Reconcile a separate sewer adjustment
- Compare an estimated statement with a catch-up read
What If Savings Simulator
- Shorter portable-heater use
- Shorten an air-conditioning schedule by two hours
- Compare an incandescent lamp with a comparable LED
- Set a timer on an idle entertainment strip
- Compare shorter sessions on an electric shower
- Model a lower-flow shower using measured power
- Avoid repeated reheats in an electric kettle
- Shorten a porch light’s overnight schedule
- Compare desktop and laptop work sessions
- Combine lower lighting wattage with shorter hours
- Compare a combined laundry and water routine
Household Water Usage Calculator
- Add daily activities for a one-person home
- Two-person shower routine
- Build a four-person household water estimate
- Estimate monthly laundry water from loads
- Compare dishwasher programs by water per cycle
- Measure the water used by a running tap
- Count full and reduced toilet flushes
- Budget for garden hose sessions
- Estimate incremental shower water for visitors
- Compare showerheads at the same duration
Water Leak Cost Estimator
- How an uncertain leak start date changes the estimate
- Measure a dripping faucet with a container
- Estimate water lost to a running toilet
- Price a hose connection leak during watering
- Bracket a leak found between weekly readings
- Compare repair dates using an observed daily water loss
- Model an intermittent leak using active time
- Combine measured losses from two fixtures
- Track a tiny loss across several billing periods
- Price the marginal units when a leak crosses a water tier
- Include volumetric sewer charges in leak costs
Hot Water Cost Calculator
- Heating 100 liters for a family
- Price one daily shower at its mixed temperature
- Convert two shower routines into monthly heated volume
- Combine hot-water demand from separate fixtures
- Compare winter and summer inlet temperatures
- Compare two outlet targets for a fixed draw
- Compare two heat-pump operating conditions
- Budget electric hot water across two rate windows
- Price a gas heater using input energy units
- Shorten a warm-water cleaning session
- Separate water and heating costs for a tub fill
Monthly Utility Tracker
- Review an electricity bill that exceeded budget
- Read a three-month electricity trend
- Compare six monthly water bills
- Check a full year of electricity and water records for gaps
- Check a shared monthly budget by utility
- Compare winter heating with spring bills
- Calculate the share of spending on water
- Record bills before and after an appliance replacement
- Compare usage and effective price across bills
- Summarize twelve months of utility spending
- Read a trend when a bill is missing