---
title: "Calculate total power consumption, electricity cost, and circuit requirements for a homelab. Enter each device's wattage to get daily/monthly/yearly kWh and cost at your local electricity rate. Accounts for cooling overhead via PUE (Power Usage Effectiveness). Shows amperage draw at 120V and 240V and warns if you exceed the NEC 80% continuous load limit on a 15A breaker. Essential for budgeting homelab operating expenses and ensuring your electrical panel can handle the load. Chain output total_watts into cooling_btu for heat load sizing."
method: POST
path: "/api/power_cost"
tags: ["homelab"]
---

# Calculate total power consumption, electricity cost, and circuit requirements for a homelab. Enter each device's wattage to get daily/monthly/yearly kWh and cost at your local electricity rate. Accounts for cooling overhead via PUE (Power Usage Effectiveness). Shows amperage draw at 120V and 240V and warns if you exceed the NEC 80% continuous load limit on a 15A breaker. Essential for budgeting homelab operating expenses and ensuring your electrical panel can handle the load. Chain output total_watts into cooling_btu for heat load sizing.

`POST /api/power_cost`

## Request

- Base URL: `https://calc.engineer`
- URL: `https://calc.engineer/api/power_cost`
- Auth: none declared

## Request body

- object
  - `devices` object[], required: List of devices with their wattage
    - `name` string: Optional label for the device (e.g. 'Dell R730')
    - `watts` number, required: Power draw of the device in watts
  - `hours_per_day` number: Hours per day the devices are running
  - `kwh_rate_cents` number: Electricity cost in cents per kilowatt-hour
  - `pue` number: Power Usage Effectiveness — ratio of total facility power to IT equipment power. 1.0 means no cooling overhead, 1.2 is typical for a home server closet, 1.5+ for poorly ventilated spaces

## Response `200`

Computed result for power_cost

- object
  - `result` object, required
    - `total_watts` number, required: Sum of all device wattages before PUE adjustment
    - `total_with_pue_watts` number, required: Total power draw including cooling overhead (watts * PUE)
    - `daily_kwh` number, required: Daily energy consumption in kilowatt-hours
    - `monthly_kwh` number, required: Monthly energy consumption in kilowatt-hours (30.44 day average)
    - `yearly_kwh` number, required: Yearly energy consumption in kilowatt-hours (365.25 day average)
    - `monthly_cost_usd` number, required: Estimated monthly electricity cost in USD
    - `yearly_cost_usd` number, required: Estimated yearly electricity cost in USD
    - `amps_at_120v` number, required: Current draw at 120V (typical North American outlet)
    - `amps_at_240v` number, required: Current draw at 240V (typical European / high-power outlet)
    - `breaker_15a_pct` number, required: Percentage of a 15A / 120V circuit used. NEC requires continuous loads stay under 80% (12A)
  - `tool` string, required
  - `version` string, required
  - `computed_at` string, date-time, required
  - `chain` object, required
    - `feeds` unknown[]
      - unknown
    - `accepts_from` unknown[]
      - unknown

## Other responses

- `400`: Validation error or invalid JSON
- `404`: Tool not found

---

[API](https://skmtc.dev/calc/apis/calc-engineer-api.md) · [All operations](https://skmtc.dev/calc/apis/calc-engineer-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calc/apis/calc-engineer-api/revisions/8830480ec488?raw)