Electricity Calculator
Calculate an appliance's electricity use and cost per day, month and year.
Inputs
Found on the appliance label or manual. Typical kettle: 1500 W. Refrigerator: 150 W.
Power consumed when plugged in but not in use. Leave 0 to skip.
Check your electricity bill or use the US average of $0.16/kWh.
Average month = 30.44 days.
Monthly Cost
$7.31
Annual Cost
$87.66
Daily Cost
$0.2400
Daily Use
1.5000kWh
Monthly Use
45.660kWh
Annual Use
547.88kWh
CO₂ Equivalent
211.5kg/year
Based on US average grid emission factor of 0.386 kg CO₂/kWh.
Step by step
Active energy (daily)
1500 W × 1 h ÷ 1000
= 1.5000 kWh/day
Total daily use
= 1.5000 kWh/day
Monthly use
1.5000 × 30.44
= 45.660 kWh/month
Monthly cost
45.660 kWh × $0.16/kWh
= $7.31/month
Yearly cost
547.88 kWh × $0.16/kWh
= $87.66/year
How it works
Energy use is calculated as watts × hours ÷ 1000 to get kilowatt-hours (kWh). An optional standby power adds a small continuous load for the hours the device is plugged in but idle. The daily kWh figure is then scaled to monthly (× 30.44) and yearly (× 365.25). Cost is simply kWh × the utility rate. The CO₂ equivalent uses the US EPA 2023 national average grid emission factor of 0.386 kg CO₂e per kWh.
Formulas
Daily kWh
Daily kWh = (watts × hours + standby_watts × (24 − hours)) ÷ 1000
- P
- Active power (W)
- t
- Hours used per day
- P_{sb}
- Standby power (W)
Cost
Annual cost = annual kWh × rate per kWh
Frequently Asked Questions
Where do I find my appliance's wattage?
Check the label on the back or bottom of the appliance, or the user manual. It may be listed as 'Rated Power' or 'Maximum Power'. If listed in amps and volts, multiply them: W = A × V.
What is the average US electricity rate?
As of 2024, the US residential average is approximately $0.16/kWh (EIA). Rates vary significantly by state — California averages ~$0.25/kWh, while Louisiana averages ~$0.10/kWh.
What is standby power?
Many appliances draw power even when not in use — TVs with remote receivers, microwaves with clocks, phone chargers, game consoles. This 'vampire' draw is typically 0.5–5 W per device but adds up across a household.
How do I lower my electricity bill?
Target the highest-wattage appliances used most often. Electric water heaters, HVAC systems and electric dryers typically dominate. Switching to LED lighting and unplugging standby devices saves a smaller but still meaningful amount.