Electricity Calculator — Free Online Energy Cost Estimator

How to Use the Electricity Calculator

1. Enter the appliance wattage: Type the power consumption of your appliance in watts into the Power Consumption field. You can find this information on the appliance label or nameplate, usually located on the bottom or back of the device. If only amperage is listed, multiply amps by voltage (typically 120V in the US) to get watts. Common wattages include 60W for LED TVs, 1,500W for space heaters, and 2,000W or more for hair dryers.
2. Set daily usage hours: Enter how many hours per day you use the appliance. For devices that cycle on and off automatically like refrigerators and air conditioners, estimate the actual run time. Refrigerators typically run about 8 hours per day even though they are plugged in 24 hours. For seasonal devices, consider averaging usage across the months you use them.
3. Adjust the billing period: Set the number of days per month that corresponds to your billing cycle. Most utility companies bill on a 30-day cycle, but this can vary. Check your electricity bill for the exact number of billing days in your most recent period. This ensures the monthly cost estimate matches your actual bill.
4. Enter your electricity rate: Type your local electricity rate in dollars per kilowatt-hour. You can find this on your monthly electricity bill, typically listed as a price per kWh in the rate breakdown section. The default value of $0.16 per kWh represents the approximate U.S. national average as of 2026, but your local rate may differ significantly.

All results update instantly as you change any input value. Try adjusting the wattage or hours to compare different appliances or usage patterns and identify opportunities to save on your electricity bill.

Electricity Cost Formula

Variables Explained

• Watts (W): The power rating of the appliance, indicating how much electrical energy it consumes per unit of time. Higher wattage means more electricity consumption. This value is printed on the appliance nameplate or in the product manual. A 100-watt device consumes energy ten times faster than a 10-watt device.
• Hours Per Day: The average number of hours the appliance runs each day. This should reflect actual usage time, not just the time the device is plugged in. For cycling appliances like HVAC systems or refrigerators, estimate the fraction of time the compressor is actively running.
• Rate Per kWh: Your electricity provider's charge for each kilowatt-hour of energy consumed. This rate varies by location, time of day (with time-of-use plans), and total consumption tier. Check your utility bill for the exact rate. Some bills include multiple rate components that should be added together for the total effective rate.
• kWh (Kilowatt-Hour): The standard unit of energy used for billing. One kWh equals 1,000 watts consumed over one hour. This is what your utility meter measures and what you pay for on your electricity bill.

Step-by-Step Example

Calculate the electricity cost of running a 1,200-watt window air conditioner for 10 hours per day at an electricity rate of $0.14 per kWh:

1. Calculate daily kWh: (1,200 x 10) / 1,000 = 12 kWh per day
2. Calculate daily cost: 12 x $0.14 = $1.68 per day
3. Calculate monthly cost (30 days): 12 x 30 x $0.14 = $50.40 per month
4. Calculate annual cost: 12 x 365 x $0.14 = $613.20 per year

Running this window AC for 10 hours daily adds about $50 per month to your electricity bill. If you reduced usage to 6 hours per day, the monthly cost drops to $30.24, saving you $241.92 annually.

Practical Examples

Example 1: David's Home Office Setup

David works from home and wants to know the electricity cost of his office equipment. He has a desktop computer (250W), a 27-inch monitor (45W), a desk lamp (15W), and a Wi-Fi router (12W) running a combined 322 watts for 10 hours per day. His electricity rate in Texas is $0.12 per kWh:

• Daily kWh: (322 x 10) / 1,000 = 3.22 kWh
• Daily cost: 3.22 x $0.12 = $0.39
• Monthly cost: 3.22 x 30 x $0.12 = $11.59
• Annual cost: 3.22 x 365 x $0.12 = $140.96

David's entire home office costs about $11.59 per month in electricity. Switching to a laptop (45W) would cut his computer-related energy use by over 80% and save approximately $90 per year.

Example 2: Maria's Pool Pump

Maria has a 1,500-watt pool pump that runs 8 hours per day during summer months. She lives in Arizona where electricity costs $0.13 per kWh. She wants to understand the seasonal cost of running her pool pump:

• Daily kWh: (1,500 x 8) / 1,000 = 12 kWh
• Daily cost: 12 x $0.13 = $1.56
• Monthly cost: 12 x 30 x $0.13 = $46.80
• Six-month summer season cost: $46.80 x 6 = $280.80

Maria's pool pump costs nearly $47 per month during summer. She is now considering a variable-speed pump that runs at 500W for 12 hours instead, which would use the same 6 kWh per day but circulate water more effectively while cutting her electricity cost in half.

Example 3: Kevin's Workshop Tools

Kevin runs a woodworking shop in his garage with a table saw (1,800W), dust collector (750W), and shop lighting (300W). He uses the workshop about 4 hours per day on weekends and 2 hours on three weekday evenings. His electricity rate in Ohio is $0.15 per kWh. He estimates an average of 2.3 hours per day over 30 days:

• Total wattage (all running simultaneously): 2,850W
• Daily kWh (averaged): (2,850 x 2.3) / 1,000 = 6.56 kWh
• Daily cost: 6.56 x $0.15 = $0.98
• Monthly cost: 6.56 x 30 x $0.15 = $29.52
• Annual cost: 6.56 x 365 x $0.15 = $359.16

Kevin spends about $30 per month powering his workshop tools. Since the table saw and dust collector do not always run simultaneously, his actual cost is likely 20% to 30% lower. He factors this into his project pricing to ensure his woodworking hobby remains cost-effective.

Example 4: Linda's Holiday Lighting

Linda puts up holiday lights every December. She uses 500 watts of outdoor LED string lights running 6 hours per night for 30 days. Her electricity rate in Vermont is $0.21 per kWh:

• Daily kWh: (500 x 6) / 1,000 = 3 kWh
• Daily cost: 3 x $0.21 = $0.63
• Monthly cost: 3 x 30 x $0.21 = $18.90

Linda's holiday lights cost about $18.90 for the entire December season. If she had used traditional incandescent lights drawing 1,500W for the same display, the cost would have been $56.70, making LEDs a clear money saver for decorative lighting.

Electricity Cost Reference Table

Table assumes an electricity rate of $0.16/kWh and 30-day month. Actual costs vary by rate and usage patterns.

Tips and Complete Guide

Understanding Your Electricity Bill

Your electricity bill contains several important pieces of information for calculating appliance costs. The per-kWh rate is the most critical number for this calculator. Many utilities use tiered pricing, where the rate increases as you consume more energy in a billing period. Time-of-use plans charge different rates depending on when you use electricity, with peak hours (typically 2 PM to 7 PM on weekdays) costing two to three times more than off-peak hours. Some bills also include demand charges, delivery fees, and taxes that add to the effective cost per kWh. For the most accurate calculator results, divide your total bill amount by total kWh consumed to get your all-in effective rate.

Using a Wattage Meter for Accurate Readings

The wattage listed on an appliance nameplate represents the maximum power draw, but many devices operate at lower wattages during normal use. A plug-in electricity usage monitor provides real-time measurements of actual power consumption. These devices cost $20 to $35 and plug into any standard outlet. Insert the monitor between the wall outlet and your appliance to measure watts, amps, kWh, and even the cost over time. This is particularly useful for devices with variable power consumption like computers, which may draw 80 watts at idle but 250 watts under heavy workload, or refrigerators that cycle between zero watts and 150 watts throughout the day.

Identifying Energy-Hungry Appliances

Heating and cooling equipment typically dominates household electricity consumption, accounting for 40% to 50% of the average American electricity bill. Water heaters add another 14% to 18%. After HVAC and water heating, the biggest electricity consumers are usually the clothes dryer, electric oven and range, refrigerator, and lighting. While individual small devices use little power, dozens of them running continuously can add up. Use our AC BTU calculator to properly size your cooling equipment and avoid energy waste from oversized or undersized units.

Common Mistakes to Avoid

• Using nameplate wattage for cycling appliances: Refrigerators, air conditioners, and furnaces cycle on and off. Using the full nameplate wattage for 24 hours greatly overestimates consumption. For refrigerators, divide the running time by roughly three. For HVAC systems, consider the duty cycle based on outdoor temperature and insulation quality.
• Ignoring standby power consumption: Many households have 20 to 40 devices drawing phantom power around the clock. A few watts each may seem insignificant, but they add up to 50 to 100 watts continuously, costing $70 to $140 per year. Use smart power strips to eliminate standby draw from entertainment centers and computer peripherals.
• Forgetting about tiered or time-of-use rates: If your utility uses tiered pricing, running high-wattage appliances pushes you into higher rate tiers faster. If on a time-of-use plan, running the dishwasher or laundry during peak hours costs significantly more. Schedule heavy energy use for off-peak times when possible.
• Not accounting for seasonal usage changes: Air conditioner and heater usage varies dramatically by season. A window AC that adds $40 per month in July costs nothing in January. Calculate costs for each season separately and average them for an accurate annual estimate rather than multiplying a summer month by twelve.
• Comparing only wattage without usage hours: A 3,000-watt clothes dryer used 1 hour per day costs less monthly than a 500-watt device running 24 hours. Total energy cost depends on both wattage and hours of operation, so always consider the full equation when comparing appliance operating costs.

Frequently Asked Questions