Electricity Cost Calculator
Calculate the cost of running an electrical appliance based on wattage, usage hours, and electricity rate.
This free online electricity cost calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
The wattage of the appliance (check the label or manual).
Check your electricity bill for your per-kWh rate.
Results
Daily Usage
0.8 kWh
Daily Cost
$$0.10
Monthly Cost
$$2.88
Yearly Cost
$$35.04
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Electricity Cost Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Electricity Cost Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Electricity Cost Calculator Formula
See calculator inputs for the governing equation
Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.
When to Use This Calculator
- •Use the Electricity Cost Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
- •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
- •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
- •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.
About This Calculator
The Electricity Cost Calculator is a free, browser-based calculation tool for engineers, students, and technical professionals. Calculate the cost of running an electrical appliance based on wattage, usage hours, and electricity rate. It implements standard formulas and supports both metric (SI) and imperial unit systems with automatic unit conversion. All calculations are performed instantly in your browser with no data sent to a server. Use this calculator as a quick reference and sanity-check tool during design, analysis, and learning. Always verify results against primary engineering references and applicable standards for any safety-critical application.
About Electricity Cost Calculator
Understanding how much your appliances cost to run is the first step toward controlling your electricity bill. The Electricity Cost Calculator converts an appliance's wattage, your daily usage hours, and your utility rate into daily, monthly, and yearly cost estimates. Many people are surprised to learn that seemingly small appliances like space heaters (1500W), gaming PCs (500W), or even old refrigerators (400W) can add hundreds of dollars to annual electricity bills. By identifying the biggest energy consumers in your home, you can make informed decisions about replacement, usage patterns, and energy-saving strategies. The calculation is straightforward: convert watts to kilowatts, multiply by hours of use, and multiply by your per-kWh electricity rate.
The Math Behind It
Formula Reference
Electricity Cost Formula
Cost = (Watts / 1000) x Hours x Rate
Variables: Watts = appliance power; Hours = daily usage; Rate = cost per kWh
Worked Examples
Example 1: Space heater running 8 hours daily
A 1500W space heater runs 8 hours per day at $0.12/kWh.
The space heater costs about $43/month or $526/year to operate.
Common Mistakes & Tips
- !Using watts instead of kilowatts (forgetting to divide by 1000), resulting in costs 1000x too high.
- !Assuming the appliance runs at full rated power continuously; many cycle on and off.
- !Using an outdated or incorrect electricity rate; rates vary by provider and plan.
Related Concepts
Used in These Calculators
Calculators that build on or apply the concepts from this page:
Frequently Asked Questions
Which appliances use the most electricity?
Air conditioning, water heaters, space heaters, clothes dryers, and electric ovens are typically the biggest consumers. A central AC system can use 3000-5000 watts when running.
Does turning off lights really save money?
Yes, though the amount depends on bulb type. Turning off a 60W incandescent for 5 hours saves about 0.3 kWh ($0.04). An LED equivalent saves about $0.006. The savings add up over a full household.