CalcaTools

Electricity Calculator | Calculate Appliance Energy Use and Cost

Calculate what your appliances cost to run from wattage, daily usage and your electricity rate — daily, monthly and yearly totals. Audit your home's energy use and find the biggest savings in your bill.

Last updated: June 2026 · Free · No sign-up required

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

ApplianceWattsDaily cost @ $0.15
LED bulb10 W$0.01 (8 h)
Fridge150 W$0.54 (24 h)
Space heater1,500 W$0.90 (4 h)

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Interpretation guide

OutputWhat it tells you
Daily costWhat the appliance costs to run each day.
kWh usedEnergy consumed per day (watts × hours ÷ 1000).
Scale upMultiply daily cost by 30 or 365 for monthly or yearly.

lightbulb Worked example

Let's say you are using the Electricity Calculator. Works out how much any electrical appliance costs to run. Enter the appliance's wattage, how many hours per day you use it, and your electricity rate per kWh, and the tool calculates the daily, Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula Cost = (watts ÷ 1000) × hours per day × rate per kWh and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: Cost = (watts ÷ 1000) × hours per day × rate per kWh

The Electricity Calculator is built on a well-established calculation method. It uses the formula Cost = (watts ÷ 1000) × hours per day × rate per kWh to turn your inputs into a reliable result. Works out how much any electrical appliance costs to run. Enter the appliance's wattage, how many hours per day you use it, and your electricity rate per kWh, and the tool calculates the daily, monthly, and yearly The steps are shown on the page so you can follow the reasoning from input to output.

Electricity cost is energy used times your tariff. Energy in kilowatt-hours is the appliance's wattage times the hours it runs, divided by 1,000.

  1. Enter the appliance power in watts.
  2. Enter how many hours per day it runs.
  3. Enter your electricity rate in dollars per kWh.
  4. The calculator finds daily kWh and multiplies by the rate for the cost.

Worked example: A 1,000 W appliance for 5 hours at $0.15/kWh costs 5 kWh × $0.15 = $0.75 per day.

Authoritative source: timeanddate.com

Frequently asked questions

How do I calculate electricity cost?
Yes — the Electricity Calculator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.
What is a kilowatt-hour?
The Electricity Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Works out how much any electrical appliance costs to run. Enter the appliance's wattage, how many hours per day you use it, and your electricity rate per kWh, and the tool calculates the daily, monthly, and yearly running cost, plus the annual energy use in There is no limit on usage, and it works on any device.
How do I find my electricity rate?
Enter the required values into the input fields and press the calculate button. The tool applies the formula Cost = (watts ÷ 1000) × hours per day × rate per kWh and returns the result with a short explanation of each step, so you can check the working yourself.
How do I get the monthly or yearly cost?
Multiply the daily cost by 30 for a typical monthly estimate and by 365 for the yearly figure. The calculator shows all three: daily, monthly, and yearly running cost. A device costing $0.90 per day adds up to about $27 monthly and $329 yearly, which is why small wattage differences compound into meaningful annual bills.
Is it free and private to use?
Yes — the calculator is completely free with no sign-up or limits, and all calculations run in your browser so your appliance data is never uploaded. CalcaTools covers its costs with display advertising. Use it to audit your appliances without creating an account or sharing personal information.
What does the Electricity Calculator do?
Works out how much any electrical appliance costs to run. Enter the appliance's wattage, how many hours per day you use it, and your electricity rate per kWh, and the tool calculates the daily, monthly, and yearly running cost, plus the annual energy use in. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.
What formula does the Electricity Calculator use?
It computes Cost = (watts ÷ 1000) × hours per day × rate per kWh, converting the appliance wattage to kilowatts first. Enter the wattage, daily usage hours, and your electricity rate and the tool returns the daily, monthly, and yearly running cost. A 1,500 W space heater used 4 hours a day at $0.15/kWh costs about $0.90 per day.
Is the Electricity Calculator free and private?
Yes — it is free with no sign-up, paywall, or usage limits, and the calculation runs entirely in your browser so nothing is uploaded. CalcaTools funds itself with display ads. The tool converts wattage and usage hours into daily, monthly, and yearly electricity costs at your rate.
How accurate is the Electricity Calculator?
The Electricity Calculator applies the standard formula: Cost = (watts ÷ 1000) × hours per day × rate per kWh. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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