Power Draw & Electricity Cost Calculator
Estimate wattage, energy consumption, and operating cost for any electrical device.
What is power draw?
Power draw is the rate at which a device uses electricity. It is usually measured in watts (W). Understanding power draw helps you estimate your electric bill, compare appliances, size a battery or inverter, and avoid overloading circuits.
If you've ever looked at an appliance label and seen terms like volts, amps, watts, or kilowatt-hours, this calculator turns those numbers into practical answers: how much energy you use and how much that usage costs over time.
Core formulas used in this calculator
1) Power (watts)
For AC loads, a common estimate is:
Watts = Volts × Amps × Power Factor
- Volts (V): electrical pressure
- Amps (A): current flow
- Power Factor (PF): efficiency of real power usage in AC systems
2) Energy usage (kilowatt-hours)
kWh = (Watts × Hours) ÷ 1000
This is the unit utility companies bill you for. A 1000 W device running for 1 hour uses 1 kWh.
3) Cost
Cost = kWh × Electricity Rate
If your rate is $0.15/kWh and you use 200 kWh/month, your monthly energy cost is about $30.00.
How to use this power draw calculator
- If you already know wattage, enter it in Known Power (Watts).
- If not, enter voltage, current, and power factor.
- Set quantity, hours per day, and days per month.
- Enter your electricity price per kWh from your utility bill.
- Click Calculate to see watts, kWh, and estimated monthly/annual costs.
Example use cases
Gaming PC
A gaming setup drawing 450 W for 5 hours/day can use significant monthly energy, especially with high local utility rates. This is useful for budgeting and deciding on energy-saving settings.
Space heater
A space heater often draws 1200-1500 W. Because wattage is high, even moderate daily runtime can heavily impact winter electricity bills.
Office equipment
Multiple monitors, networking gear, and always-on peripherals add up over time. Use quantity and runtime fields to estimate true total load.
Tips to reduce electricity consumption
- Choose ENERGY STAR or high-efficiency appliances.
- Reduce standby and idle time by using smart strips or timers.
- Lower runtime where practical (lighting, HVAC fan-only cycles, unused electronics).
- Upgrade old motors and compressors to variable-speed models.
- Track high-load devices first—heaters, dryers, ovens, pumps, and air conditioning.
Quick FAQ
Is watts the same as kWh?
No. Watts measure instant power; kWh measures energy over time.
What is a good power factor to use?
For resistive loads (heaters/incandescent bulbs), use around 1.0. For many motor/electronic loads, values like 0.8-0.95 are common.
Can this calculator help with breaker planning?
Yes, as a rough guide. It also estimates current draw when voltage is available. For final electrical design, always follow local code and consult a licensed electrician.