The cost is calculated using the formula: Daily Cost = (Power in Watts × Hours per Day ÷ 1000) × Rate per kWh. This converts watt-hours to kilowatt-hours (kWh), which is the unit used by utility companies for billing. Weekly cost = Daily × 7, Monthly = Daily × 30, Yearly = Daily × 365.

A kilowatt-hour (kWh) is a unit of energy equal to using 1,000 watts for one hour. For example, a 100-watt light bulb running for 10 hours consumes 1 kWh (100W × 10h = 1,000 watt-hours = 1 kWh). Your electricity bill is based on the total number of kWh you consume each billing period.

Refrigerators cycle on and off throughout the day — they don't run the compressor continuously. While plugged in 24 hours, the actual compressor runtime is typically 30–50% of the day (about 8–12 hours). Our calculator uses the average power draw (around 150W) to account for this cycling. For appliances with duty cycles (fridges, AC units, dehumidifiers), use the average wattage rather than peak.

You can find the wattage on the appliance's rating label or nameplate (usually on the back or bottom). Look for "W" or "Watts." If only amps (A) and volts (V) are listed, multiply them: Watts = Amps × Volts. You can also use a plug-in power meter (like Kill A Watt) for the most accurate real-world measurement.

Rates vary significantly by region. Approximate residential rates (as of 2024): USA: $0.10–$0.20/kWh (avg. ~$0.14), UK: £0.25–£0.35/kWh, EU: €0.15–€0.35/kWh, Australia: A$0.25–A$0.40/kWh, India: ₹4–₹10/kWh. Check your latest utility bill for your exact rate — it's usually listed clearly.

Yes! Add as many appliances as you like using the form. Each appliance appears in your list with its individual cost breakdown. The total combined cost across all appliances is displayed in the summary cards. You can also see a per-appliance monthly cost breakdown with progress bars showing each device's share of the total.

Yes! Many devices consume power even when "off" — this is called standby power or vampire energy. TVs, game consoles, chargers left plugged in, and microwaves with clocks can each draw 1–10 watts continuously. Across multiple devices running 24/7, this can add $50–$150+ per year to your bill. Use our calculator with small wattages (3–10W) and 24 hours to estimate your standby losses.

We use the global average carbon intensity of 0.475 kg CO₂ per kWh (based on IEA data). Actual emissions depend on your local energy mix — countries relying heavily on coal (e.g., India, China, parts of the US) may have higher intensities (0.6–0.9 kg/kWh), while regions with renewables + nuclear (e.g., France, Norway) may be much lower (0.02–0.1 kg/kWh). This is an estimate for awareness, not a precise measurement.