Energy Consumption Calculator
Plan your hvac & plumbing project with our free energy consumption calculator. Get precise measurements, material lists, and budgets.
Reviewed by Abdullah, Technical Content Specialist
Formula
kWh = (Watts x Hours) / 1,000 | Cost = kWh x Rate per kWh
Energy in kilowatt-hours equals the device wattage multiplied by the hours of operation, divided by 1,000. Multiply the kWh by your electricity rate (cost per kWh) to get the energy cost. For multiple identical devices, multiply the total wattage by the quantity before calculating.
Worked Examples
Example 1: Space Heater Monthly Cost
Problem:A 1,500W space heater runs 8 hours/day for 30 days at $0.13/kWh.
Solution:Daily kWh = 1,500 / 1,000 x 8 = 12 kWh\nMonthly kWh = 12 x 30 = 360 kWh\nMonthly cost = 360 x $0.13 = $46.80
Result:$46.80 per month
Example 2: LED vs Incandescent Bulbs
Problem:Compare 10 LED bulbs (10W each) vs 10 incandescent (60W each) running 6 hrs/day for 30 days at $0.13/kWh.
Solution:LED: 100W x 6 x 30 / 1,000 = 18 kWh = $2.34/mo\nIncandescent: 600W x 6 x 30 / 1,000 = 108 kWh = $14.04/mo\nSavings = $11.70/mo
Result:LED saves $11.70 per month ($140.40 per year)
Frequently Asked Questions
How do I calculate energy consumption in kWh?
Multiply the device wattage by the number of hours it runs, then divide by 1,000 to convert watts to kilowatts. For example, a 1,500-watt heater running 8 hours uses 1,500 times 8 divided by 1,000 equals 12 kWh per day. Multiply by the number of days in a month for monthly consumption. Check the device label or manual for its rated wattage, which is usually listed on a sticker on the back or bottom.
References
Reviewed by Abdullah, Technical Content Specialist · Editorial policy