Last updated: March 2026
What Is an Electricity Cost Calculator?
An electricity cost calculator estimates how much money you spend running a specific appliance or device. Every electrical device has a wattage rating that tells you how much power it draws. By combining that wattage with how many hours you use the device and your local electricity rate, you can calculate the exact cost per day, per month, and per year.
Understanding your electricity costs is the first step toward reducing your energy bill. Many homeowners are surprised to discover that small appliances used for many hours (like a dehumidifier or gaming PC) can cost more annually than high-wattage devices used briefly (like a toaster or hair dryer). This calculator makes those hidden costs visible instantly.
How to Use This Calculator
Step 1: Enter the wattage. Choose from 24+ common appliance presets or type in a custom wattage. You can find the wattage on a label near the device's power cord, in the owner's manual, or by searching the model number online.
Step 2: Set your usage. Adjust the hours-per-day and days-per-month sliders to match how you actually use the appliance. A bedroom TV might run 4 hours a day, while a refrigerator runs 24/7.
Step 3: Set your rate. Select your state from the dropdown to auto-fill the average residential rate, or enter your exact rate from your electricity bill. Results update in real-time as you adjust any input.
Step 4: Compare appliances. Click "Add Another Appliance" to compare up to 5 devices side by side. See which ones cost the most and identify the best opportunities to save money on your electricity bill.
Key Features
24+ Appliance Presets: Quickly select from common household devices including lighting, kitchen appliances, HVAC systems, electronics, and more. Each preset includes the typical wattage for that appliance type.
All 50 State Rates: Average residential electricity rates for every US state and Washington DC are built in. Select your state and the rate auto-fills, or override with your exact rate from your bill.
Compare Mode: Add up to 5 appliances and see individual and combined costs. This is perfect for estimating the total electricity cost of a home office, entertainment center, or entire kitchen.
Copy Summary: One click copies a plain-text summary of your calculation, perfect for sharing with roommates, landlords, or for your own records.
The Electricity Cost Formula
The formula is straightforward. First, convert watts to kilowatts by dividing by 1,000. Then multiply by usage hours to get kilowatt-hours (kWh), which is the unit your utility company charges you for. Finally, multiply kWh by your rate.
Daily kWh = (Watts x Hours per Day) / 1,000. Daily Cost = Daily kWh x Rate. Monthly Cost = Daily kWh x Days per Month x Rate. Annual Cost = Daily kWh x 365 x Rate.
For example, running a 1,500W space heater for 8 hours per day at $0.16/kWh: Daily kWh = (1,500 x 8) / 1,000 = 12 kWh. Daily cost = 12 x $0.16 = $1.92. Monthly cost (30 days) = $57.60. Annual cost = $700.80.
Frequently Asked Questions
How do I find my electricity rate?
Check your most recent electricity bill for a line labeled "Energy Charge," "Price to Compare," or "Cost per kWh." It is usually between $0.10 and $0.30/kWh depending on your state. If you cannot find it, select your state from the dropdown and we will use the average residential rate for your state.
How does compare mode work?
Click "Add Another Appliance" to compare up to 5 appliances side by side. Each appliance gets its own card with independent wattage, hours, and rate settings. A combined total shows the sum of all running costs at the bottom.
How accurate is this calculator?
The calculator is mathematically precise for the wattage and usage hours you enter. Real-world costs may vary slightly because some appliances (like refrigerators and AC units) cycle on and off rather than running at full wattage continuously. For cycling appliances, actual costs are typically 30-50% of the calculated maximum.
Where do the state electricity rates come from?
State average residential electricity rates are sourced from the U.S. Energy Information Administration (EIA). All 50 states plus Washington DC are included. Rates are updated periodically. Your actual rate may differ based on your utility provider, usage tier, and rate plan.
What uses the most electricity in a home?
Central air conditioning (3,500W), electric dryers (3,000W), and EV chargers (7,200W) are typically the biggest energy consumers. However, total cost also depends on hours of use. A refrigerator at 150W running 24/7 can cost more annually than a dryer used for 1 hour a day.
How can I reduce my electricity bill?
Switch to LED bulbs, unplug devices when not in use (phantom loads cost $100-200/year), use a smart power strip, set your thermostat 2 degrees higher in summer and lower in winter, run dishwashers and laundry during off-peak hours, and consider a time-of-use rate plan from your utility.