# Electricity Cost Calculator

- **URL:** https://codeasystem.com/calculators/everyday/electricity-cost-calculator/
- **Category:** everyday
- **Description:** See what any appliance costs to run per day, month and year from its wattage and your electricity rate.
- **Primary output:** Cost per day: $1.35

## Inputs
- Device wattage (name: `watts`, type: number, example: 1500)
- Hours used per day (name: `hours`, type: number, example: 6)
- Electricity rate (name: `rate`, type: number, prefix: $, example: 0.15)

## Outputs
- Cost per day: $1.35
- Energy used per day: 9 kWh
- Cost per month (30 days): $40.50
- Cost per year (365 days): $492.75

## Formula / methodology
```
kWh/day = watts × hours ÷ 1000
Cost/day = kWh/day × rate     Month = ×30 days     Year = ×365 days
```

A watt is already joules per second, so energy in kilowatt-hours is simply watts times hours divided by 1,000. Multiplying daily energy by your utility rate gives daily cost, which we extend to 30-day months and 365-day years.

## Assumptions & limitations
- Flat rate per kWh; time-of-use plans charge more at peak hours.
- Steady power draw; devices with thermostats cycle on and off.
- Standby (“vampire”) draw outside the entered hours is not counted.

## How to use
1. **Find the wattage**; Check the appliance label, its spec sheet, or a plug-in power meter for the true draw.
2. **Estimate daily hours**; Be honest about actual runtime; a heater with a thermostat may run half the time it is switched on.
3. **Enter your rate**; Your bill’s price per kWh is printed near the usage totals; divide the supply-plus-delivery total by kWh if unsure.

## Example
A 1500 W space heater running 6 hours a day at $0.15 per kWh burns 9 kWh daily; $1.35 a day, about $40.50 a month or $492.75 a year.

Result for these inputs:

```
Cost per day: $1.35
```

## About this calculator
### Heat is expensive; light is cheap

Anything that resists electricity to make heat; heaters, dryers, kettles; draws 1,500–5,000 W and dominates bills. LEDs draw under 15 W, so even leaving lights on rarely matters by comparison.

### The delivery-charge surprise

Many bills split generation from delivery. Your true per-kWh cost is the sum of both, which can be double the advertised generation rate. Use the all-in figure here.

### Idle load adds up

Devices drawing 5 W around the clock consume 44 kWh a year; small, but multiplied across a house full of chargers and set-top boxes it becomes a quiet line item worth killing.

## FAQs
### Where do I find my kWh rate?

It is itemized on your utility bill. Add supply/generation and delivery charges per kWh for the complete picture; US residential averages hover near $0.15–$0.17.

### How do I measure an unknown device?

A plug-in power meter measures actual draw including standby modes, usually costing less than the savings it uncovers in a year.

### Do old fridges really cost more?

Yes; pre-2000 refrigerators can draw two to three times as much as modern efficient units, making replacement one of the fastest energy paybacks in a home.

## Related calculators
- [Fuel Cost Calculator](https://codeasystem.com/calculators/everyday/fuel-cost-calculator/)
- [Percentage Calculator](https://codeasystem.com/calculators/math/percentage-calculator/)

---
Last updated: 2026-08-23 · Version: 1.0.0 · [HTML version](https://codeasystem.com/calculators/everyday/electricity-cost-calculator/)