Calculate electricity cost, energy usage, and annual power consumption for appliances and devices. Compare wattage, kWh, and utility bills.
Understanding how much electricity your appliances and devices consume is the first step toward lower utility bills and a smaller carbon footprint. Every watt matters when multiplied across hours, days, and months of continuous use. Even small always-on loads become noticeable once you annualize them. That is why standby power often surprises people when they total a whole house.
This power consumption calculator takes any device's wattage, daily usage hours, and your electricity rate to compute daily, monthly, and annual energy use in kilowatt-hours (kWh) and dollars. It also estimates CO₂ emissions based on your grid's carbon intensity and compares the running cost of different devices side by side.
Whether you're auditing your home's energy use, evaluating whether to upgrade to an energy-efficient appliance, or estimating the operating cost of a new device, this calculator provides all the numbers. The device preset library covers common household appliances so you can get instant estimates without looking up wattage specs.
Use this calculator when you want to turn wattage into a real energy bill estimate. It is useful for comparing appliances, checking standby loads, and spotting devices that cost more to run than they should. That makes it useful for purchase decisions as well as for simple home energy audits.
Energy (kWh) = Watts × Hours / 1000. Cost = kWh × Rate. Annual cost = daily cost × 365. CO₂ = kWh × emission factor.
Result: 0.80 kWh/day, $0.096/day, $35.04/year
A 100W device running 8 hours per day uses 0.80 kWh daily, costing about $0.10 per day or $35 per year at $0.12/kWh.
Your electricity bill charges by the kilowatt-hour (kWh). To calculate any device's cost, multiply its wattage by the hours used, divide by 1,000 to get kWh, then multiply by your rate. Most US households use 900-1,100 kWh per month, paying $100-150. The biggest consumers are HVAC systems (40-50%), water heaters (12-18%), and large appliances (refrigerator, washer, dryer) at 10-15%.
When comparing appliances, look beyond the purchase price to the total cost of ownership. An energy-efficient refrigerator costing $200 more but using 200 fewer kWh/year saves $25-30/year, paying for itself in 7-8 years while lasting 15-20 years total. The same logic applies to HVAC systems, water heaters, and lighting.
Every kWh of electricity produces CO₂ depending on your grid's generation mix. In the US, the average is 0.42 kg CO₂/kWh. Switching to renewable energy or simply reducing consumption has a measurable climate impact. A household using 10,000 kWh/year produces about 4.2 metric tons of CO₂ — equivalent to driving 10,000 miles in an average car.
Check the label on the appliance, the user manual, or the manufacturer's website. For variable-load devices like fridges, use the estimated annual kWh from the EnergyGuide label.
A kilowatt-hour is 1,000 watts running for one hour. It's the standard unit for measuring electricity consumption on utility bills.
The US average is about $0.12-0.16/kWh. Rates vary by state — Hawaii is ~$0.35/kWh while Louisiana is ~$0.10/kWh. Check your latest utility bill for your exact rate.
Many devices draw "standby" or "phantom" power when off but plugged in. TVs, chargers, and game consoles typically draw 1-10W in standby.
The US average is about 0.42 kg CO₂ per kWh. Clean grids (hydro/nuclear) can be as low as 0.05 kg/kWh, while coal-heavy grids exceed 0.90 kg/kWh.
Heating/cooling and water heating account for 50%+ of home energy. Upgrading insulation, using a smart thermostat, and switching to LED lighting are the biggest wins.