How to Calculate Your Electricity Cost (Formula + Examples)

By Jorge Sanchez · April 20, 2026 · 5 min read

Bottom line: Cost = (Watts ÷ 1,000) × Hours Used × Your kWh Rate. The national average rate is $0.16/kWh. A 100W light bulb on for 10 hours costs $0.16.

Want to know why your electric bill is so high? Or whether that space heater is worth it? The formula to calculate the cost of running any appliance is straightforward — you just need three numbers.

The Formula

kWh used = (Watts ÷ 1,000) × Hours

Cost = kWh × Price per kWh

Find your kWh rate on your electricity bill (usually $0.10–$0.30 depending on your state). The national average in the U.S. is about $0.16/kWh.

Examples

Space Heater (1,500W)

Daily cost = (1,500 ÷ 1,000) × 8 hrs × $0.16 = $1.92/day
Monthly cost = $1.92 × 30 = $57.60/month

Central AC (3,500W)

Daily cost = (3,500 ÷ 1,000) × 10 hrs × $0.16 = $5.60/day
Monthly cost = $5.60 × 30 = $168/month

Laptop (65W)

Daily cost = (65 ÷ 1,000) × 8 hrs × $0.16 = $0.083/day
Monthly cost = $0.083 × 30 = $2.50/month

Common Appliance Costs Per Month

Appliance	Watts	Hrs/Day	Monthly Cost
Central AC	3,500	10	$168
Electric water heater	4,000	3	$58
Electric dryer	5,000	1	$24
Refrigerator	150	24	$17
Dishwasher	1,800	1	$9
TV (55-inch LED)	100	5	$7
Desktop computer	200	8	$8
LED light bulb	10	8	$0.38

Calculated at $0.16/kWh national average.

The Biggest Energy Hogs

In a typical American home, these systems dominate the electric bill:

Heating & cooling: 40–50% of energy use
Water heating: 12–18%
Large appliances (washer, dryer, fridge): 13%
Lighting: 9%
Electronics: 4%

If you want to cut your bill, your HVAC is where to focus first. Even a 10% efficiency improvement can save $15–$30/month.

Electricity Cost Calculator

Enter watts, hours per day, and your rate to calculate daily, monthly, and annual costs.

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Jorge Sanchez · Live Event Production Specialist · CalQpro