How to Calculate Power Consumption
Every electrical device has a wattage rating — the amount of power it draws when running. To calculate your total power consumption and electricity cost, use these formulas:
Daily kWh = (Watts × Qty × Hours/Day) ÷ 1000
Monthly kWh = Daily kWh × Billing Days
Monthly Cost = Monthly kWh × Rate per kWh
Annual Cost = Daily kWh × 365 × Rate per kWh
What Is Watt vs kWh?
A watt (W) measures the rate of energy use at any moment — like a speedometer. A kilowatt-hour (kWh) measures total energy consumed over time — like an odometer. A 1,000W device running for 1 hour uses 1 kWh, which is what your utility company bills you for.
How Much Does the Average Home Use?
An average US household uses about 886 kWh per month. Heating and cooling (HVAC) accounts for nearly half of that. By tracking each device with our power consumption calculator, you can identify which appliances are driving your electricity bill.
What Is a Safe Circuit Load?
A standard 15-amp, 120V household circuit has a maximum capacity of 1,800 watts. For safety, never exceed 80% of that (1,440W). Our circuit load monitor warns you when your device list approaches those thresholds.
Frequently Asked Questions
How do I find the wattage of my devices?
Check the label on the back or bottom of the device, the user manual, or the manufacturer's website. Wattage is usually listed as "W" or can be calculated from amps × volts (e.g. 2A × 120V = 240W).
What uses the most electricity in a home?
HVAC (heating/cooling) typically accounts for 45–50% of a home's electricity. Electric water heaters, clothes dryers, and electric ovens are the next biggest consumers, each using 3,000–5,000 watts.
How many kWh does a TV use per month?
A modern 55" LED TV uses about 80W. Watching 5 hours/day = 0.4 kWh/day = 12 kWh/month. At $0.16/kWh that's about $1.92/month — quite affordable compared to HVAC.
How can I reduce my power consumption?
Focus on your biggest consumers first: upgrade to a smart thermostat, improve home insulation, switch to LED lighting, use Energy Star appliances, and eliminate phantom loads by unplugging devices on standby. Even small changes on high-wattage devices have a big impact.
Is this power consumption calculator free?
Yes — 100% free, no sign-up required. It runs entirely in your browser and supports 150+ global currencies with live exchange rates.