Electricity Cost of Appliance Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Everyday & Life

Tranche

tranche-4

Evidence ID

t4-258

Ledger rows

1

No ledger note is attached.

Review findings

The core energy and cost formulas are standard and correct under the stated units. Review is required to define the exact monthly and annual day-count conventions and to explicitly include hours_per_day × days in the total-energy formula. The honest-label warning about efficiency, duty cycle, and manually entered rates is appropriate; preset values should also identify their source and reference date.

Formula and scope findings

• kWh = watts × hours / 1000 is correct when hours means total operating hours, but the declared input is hours/day plus days; the aggregation formula must explicitly be total_kWh = watts × hours_per_day × days / 1000.
• The mapping of days to monthly and annual outputs is unspecified: a month could mean 28–31 calendar days or a fixed 30-day period, and an annual result could mean 365 or 366 days.
• Daily cost is implied but not explicitly stated as daily_kWh × rate_per_kwh; the output definitions should specify whether monthly and annual values are derived from daily usage or from separately entered total hours.

Unit assumptions

• Wattage is in watts (W), hours/day is decimal operating hours per day, and days is a count of days in the reporting period.
• Dividing by 1000 converts watt-hours to kilowatt-hours.
• Electricity rate is in dollars per kilowatt-hour ($/kWh), so cost is in dollars.
• For the test vectors, a monthly period means exactly 30 days and an annual period means exactly 365 days.
• Inputs represent actual energized operating time; standby consumption, variable power draw, and duty cycle are not modeled unless separately incorporated into the wattage or hours.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

An extreme but numerically representable wattage causes JavaScript arithmetic overflow: 1e308 × 24 becomes Infinity, and all derived outputs become Infinity. The instrument should validate finite, reasonable inputs and reject or clearly report overflow.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "appliance_wattage_w": 1500,
    "hours_per_day": 2,
    "electricity_rate_usd_per_kwh": 0.18,
    "days": 30,
    "period": "monthly"
  },
  "expected_outputs": {
    "daily_kwh": 3,
    "daily_cost_usd": 0.54,
    "period_kwh": 90,
    "period_cost_usd": 16.2
  },
  "working": "Daily energy = 1500 W × 2 h/day ÷ 1000 = 3000 Wh/day ÷ 1000 = 3 kWh/day. Daily cost = 3 kWh/day × $0.18/kWh = $0.54/day. Period energy = 3 kWh/day × 30 days = 90 kWh. Period cost = 90 kWh × $0.18/kWh = $16.20."
}

Related workflows

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json