Introduction
This Power Consumption Calculator shows how much electricity your appliances use and what they cost. Pick an appliance, set its watts, how long it runs, and how many you own. The calculator gives you energy use and cost per day, month, and year.
You can add as many appliances as you want. Presets fill in typical wattage for things like fridges, air conditioners, LED bulbs, TVs, and EV chargers. You can change any number to match your own devices.
The tool also estimates your yearly CO₂ emissions, shows a chart comparing appliances, and lists every step of the math. Use it to find which devices cost you the most and where you can save on your power bill. If you only need a quick bill estimate for a single device, the Electricity Cost Calculator is a faster route, and the Carbon Footprint Calculator puts your household emissions in a wider context.
How to use our Power Consumption Calculator
Enter your electricity rate and add each appliance you want to check. The calculator shows how much energy each one uses per day, month, and year, what it costs, and how much CO₂ it makes.
Electricity Rate (per kWh): Type the price you pay for one kilowatt-hour. You can find this on your power bill. Most U.S. homes pay about $0.13 to $0.17. Pick your currency symbol from the drop-down next to it. If your rate is quoted in another currency, the Currency Calculator can help you convert it first.
Energy Display Unit: Choose how you want energy shown, like kWh, Wh, MWh, MJ, BTU, or therms. Costs are always worked out in kWh. For other unit swaps, see the Unit Converter Calculator.
Grid Emissions Factor (kg CO₂/kWh): Type how much carbon dioxide your power grid makes per kWh. The U.S. average is 0.386. Leave it as is if you are not sure.
Month Length Basis: Pick how many days count as one month. Use 30.4 for a normal year average, or pick 30 or 31 to match your bill.
Appliance preset: Pick an item from the list, like a fridge or a TV. It fills in typical power, load, and run time for you. Choose "Define your own" to type your own numbers.
Appliance name / label: Give the item a name so you can spot it in the chart, like "Kitchen Fridge" or "Bedroom TV".
Rated power: Type the watts listed on the appliance label or manual. Then pick the unit: watts, kilowatts, BTU/h, horsepower, or tons. If your label only lists amps and volts, run the numbers through the Amps to Watts Calculator first.
Capacity %: Type how hard the item works, from 0 to 100. Use 100 if it runs at full power. Use a lower number for things that cycle on and off, like a fridge.
Quantity: Type how many of the same item you have. For example, put 12 for twelve LED bulbs.
Usage: Type how long the item runs, then pick the time period, such as hours per day, hours per week, or days per month. The tool turns this into average hours per day.
Adjust within typical range: If you picked a preset, slide this bar to set a wattage inside the normal range for that item. The power box updates as you slide.
Add Appliance: Click this to add another row and build a full list for your home. Click Remove to delete a row you don't need.
Calculate and Reset: Click Calculate to check your entries and see the totals, chart, and step-by-step math. Click Reset to start over with the sample list.
What Is Power Consumption?
Power consumption is how much electricity a device uses. Power is measured in watts (W). A watt tells you how fast a device pulls energy right now. A 60 W light bulb uses energy twice as fast as a 30 W bulb. The Power Calculator and the Wattage Calculator explain the underlying relationship between voltage, current, and watts.
Energy is power used over time. It is measured in kilowatt-hours (kWh). One kilowatt-hour means 1,000 watts running for one hour. Your power company bills you for kWh, not watts.
The Basic Formula
To find energy use, multiply power by time:
Energy (kWh) = Watts ÷ 1,000 × Hours used
Example: a 100 W fan running 5 hours a day uses 100 ÷ 1,000 × 5 = 0.5 kWh per day. Over 30 days that is 15 kWh. At $0.15 per kWh, it costs about $2.25 a month.
Rated Power vs. Real Power
The number on a label is the rated power. It is the most the device can pull. Many machines do not run full blast all the time. A fridge stays plugged in 24 hours, but its motor only kicks on part of the time. That is why a "capacity percent" is used. A fridge rated at 250 W running at 35% capacity really draws about 88 W on average. For motor-driven gear, the kW Calculator and the Power Factor Calculator help you separate nameplate ratings from real draw.
What Uses the Most Power
Things that make heat or cold are the biggest users. Air conditioners, heaters, water heaters, clothes dryers, and ovens can use 1,000 to 5,000 watts. Small gadgets like phone chargers, LED bulbs, and laptops use very little. Running a 1,500 W heater for one hour uses as much energy as a 10 W LED bulb running for 150 hours. To size cooling and heating loads properly, try the AC Tonnage Calculator, the BTU Calculator, or the Heat Loss Calculator. Gamers sizing a rig can check the PSU Calculator.
Electricity Cost and CO₂
Your bill is simple math: kWh used × price per kWh. In the United States, homes pay about $0.13 to $0.17 per kWh, but rates change a lot by state and season. Check your bill for your real rate. Once you know your monthly total, the Monthly Budget Calculator and the Cost of Living Calculator help you plan around it.
Making electricity often burns fuel, which releases carbon dioxide. The U.S. average is about 0.386 kg of CO₂ per kWh. Grids that use more wind, solar, hydro, or nuclear power have a much lower number. The Ecological Footprint Calculator puts these numbers into everyday terms.
Ways to Use Less
- Swap old bulbs for LEDs. They use about 85% less power.
- Set the thermostat a few degrees closer to the outside temperature.
- Wash clothes in cold water and air dry when you can.
- Unplug chargers and game consoles, or use a power strip. Standby draw adds up.
- Look for the Energy Star label when buying new appliances.
- Cover part of your load with rooftop panels — size a system with the Solar Panel Calculator or the broader Solar Calculator.
- Planning for outages? The Generator Sizing Calculator uses the same connected-load figure this tool reports.
Handy Units
- 1 kW = 1,000 watts
- 1 MWh = 1,000 kWh
- 1 kWh = 3.6 MJ = about 3,412 BTU
- 1 hp ≈ 735.5 watts — see the Horsepower Calculator
- 1 ton of cooling ≈ 3,517 watts
Related Electrical Calculators
- Ohms Law Calculator — solve for volts, amps, resistance, and watts.
- Watts to Amps Calculator — convert appliance wattage into circuit current.
- Amp Calculator — check whether a circuit can handle a load.
- Wire Size Calculator and Voltage Drop Calculator — for wiring new appliance circuits.
- kW to Amps Calculator and kVA Calculator — for larger or commercial loads.
- 3 Phase Power Calculator — for shop and industrial equipment.