Source: https://guthlabs.ai/docs/instruments/electricity-cost-of-appliance-calculator/implementation/

instrument implementation / implementation-contract

# Electricity Cost of Appliance Calculator implementation

A source-bound implementation contract for Electricity Cost of Appliance Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-258

**Effect**: Computation or source lookup only

## Input and validation requirements

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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/electricity-cost-of-appliance-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/electricity-cost-of-appliance-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/electricity-cost-of-appliance-calculator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`