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Electricity Cost Calculator
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Actual power: 0.00 W
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Power Consumption
Actual Power: 0.00 W
Energy per hour: 0.00 kWh
Daily energy: 0.00 kWh
Cost Breakdown
Cost per hour: $0.00
Weekly cost: $0.00
5-year cost: $0.00
Formula Used
Energy (kWh) = (Power (W) × Hours × Capacity%) / 1000
Cost = Energy (kWh) × Price per kWh
Energy Saving Tips
Monitor your energy habits and turn off unused appliances
Replace incandescent bulbs with LED lights (75W → 9W)
Install programmable thermostats for heating/cooling
Choose energy-efficient appliances when shopping
Improve home insulation (windows, doors, walls)
Use curtains/blinds to reduce heating and cooling needs
Understanding Units of Electricity
One of the most common units of electrical power for appliances is the watt (W). Other common units of power include kilowatts (kW), British thermal units (BTU),horsepower (hp), and tons. Understanding these units helps you accurately estimate energy consumption and costs for various appliances in your home or business.
Watts, Kilowatts and Kilowatt-Hours
Watts (W) is a unit of power used to quantify the rate of energy transfer. It is defined as 1 joule per second. A kilowatt is a multiple of a watt. One kilowatt (kW) is equal to 1,000 watts. Both watts and kilowatts are SI units of power and are the most common units of power used worldwide.
Kilowatt-hours (kWh) are a unit of energy. One kilowatt-hour is equal to the energy used to maintain one kilowatt of power for one hour. Generally, when discussing the cost of electricity, we talk in terms of energy. Energy (E) and power (P) are related to each other through time (t):
Electricity is most often measured and paid for based on the number of kilowatt-hours used. The reason that kilowatt-hours are typically used as a measurement of energy rather than watt-hours is simply because of scale: the amount of energy a typical household in the United States uses in a year is on the order of millions of watt-hours, so it is easier to discuss in terms of kilowatt-hours instead.
Example Calculation:
If you run a 1,000 W (1 kW) appliance for 5 hours, you consume:
1 kW × 5 hours = 5 kWh of energy
At $0.15 per kWh, this costs:
5 kWh × $0.15 = $0.75
BTU and BTU/h
British thermal units (BTU) are a measurement of heat used as part of the Imperial and US customary units of measurement. It is defined as the amount of heat that is required to increase the temperature of 1 pound of water by 1 degree Fahrenheit. Heat is a type of energy, so BTU can be directly compared to other measurements of energy such as joules (SI unit of energy), calories (metric unit), and kilowatt-hours (kWh).
Conversion Factors:
- 1 BTU = 0.2931 watt-hours
- 1 BTU = 0.0002931 kWh
- 1 kWh ≈ 3,412 BTU
BTU/h, BTU per hour, is a unit of power that represents the energy transfer rate of BTU per hour. BTU/h is often abbreviated to just BTU to represent the power of appliances. For example, an air conditioner marked with a label of 12,000 BTU actually has an energy transfer rate of 12,000 BTU per hour.
Practical Example:
A 12,000 BTU/h air conditioner is equivalent to:
12,000 × 0.2931 = 3,517 watts (3.517 kW)
Running it for 8 hours per day costs (at $0.15/kWh):
3.517 kW × 8 hours × $0.15 = $4.22 per day
Horsepower
Horsepower (hp) is a unit of power most commonly used to reference the output of engines or motors. There are a number of different definitions of horsepower. Two of the most common are mechanical horsepower and metric horsepower.
Conversion Factors:
- 1 mechanical horsepower = 745.7 watts
- 1 metric horsepower = 735.5 watts
The term "horsepower" was developed by James Watt, who compared the output of steam engines to the power of draft horses based on how many times a horse could turn a mill wheel in an hour. This historical measurement unit continues to be used today, particularly in the automotive and industrial sectors.
Example Calculation:
A 2 hp electric motor is equivalent to:
2 × 745.7 = 1,491.4 watts (1.49 kW)
Running continuously for 24 hours costs (at $0.15/kWh):
1.49 kW × 24 hours × $0.15 = $5.36 per day
Ton (Refrigeration)
There are many different definitions of a ton that are related to the measurement of weight. In the context of power, the "ton" refers to the ton of refrigeration. The ton of refrigeration is defined as the rate of heat transfer necessary to melt 2,000 pounds (1 short ton) of pure ice at 0°C in 24 hours. It is used mainly in the United States to describe how well refrigerators and air conditioners extract heat.
Conversion Factors:
- 1 ton ≈ 3,517 watts (3.517 kW)
- 1 ton ≈ 12,000 BTU/h
This unit is particularly useful when discussing commercial refrigeration systems and large air conditioning units. A typical home air conditioner might be rated at 2-5 tons, while large commercial systems can be 20 tons or more.
Example Calculation:
A 3-ton air conditioning system is equivalent to:
3 × 3,517 = 10,551 watts (10.55 kW)
Running it for 6 hours per day costs (at $0.15/kWh):
10.55 kW × 6 hours × $0.15 = $9.50 per day
Monthly cost: $9.50 × 30 = $285 per month
Energy Usage by Common Appliances
Below is a comprehensive table showing the estimated energy requirements of various appliances. It is important to note that the requirements listed on the packaging of an appliance generally reflect the maximum energy requirements. Typical usage of the appliance likely results in far lower energy use than stated, so actual consumption cannot be calculated directly as power requirement × time without considering duty cycles and usage patterns.
Home Appliances
Kitchen Appliances
Electronics & Personal
Large Appliances
Practical Cost Examples
Example 1: LED vs Incandescent
Scenario: Lighting a room 5 hours/day
Incandescent (60W):
Daily: 60W × 5h = 0.3 kWh → $0.045/day
Yearly: 109.5 kWh → $16.43/year
LED (9W):
Daily: 9W × 5h = 0.045 kWh → $0.007/day
Yearly: 16.4 kWh → $2.46/year
Example 2: Refrigerator (24/7)
750W refrigerator running continuously
Note: Duty cycle ~30-40%
Actual power: 750W × 35% = 262.5W
Daily: 262.5W × 24h = 6.3 kWh
Daily cost: 6.3 kWh × $0.15 = $0.95/day
Cost Breakdown:
Monthly: $28.35
Yearly: $346.18
10-year cost: $3,461.80
Example 3: Central AC (Summer)
3-ton (10,551W) AC running 8 hours/day
Summer months (June-August):
Daily: 10.55 kW × 8h = 84.4 kWh
Daily cost: 84.4 × $0.15 = $12.66/day
3-Month Summer Cost:
Monthly: $379.80
3 months total: $1,139.40
Example 4: Electric Vehicle
7.5kW Level 2 charger, 2 hours/day
Daily charging (40 miles range):
Daily: 7.5 kW × 2h = 15 kWh
Daily cost: 15 × $0.15 = $2.25/day
Annual EV Costs:
Monthly: $67.50
Yearly: $821.25
Cost per mile: $0.056/mile
Advanced Energy Saving Strategies
Peak vs Off-Peak
Many utilities offer time-of-use rates. Running high-power appliances (dishwasher, laundry, EV charging) during off-peak hours (typically 9 PM - 6 AM) can save 30-50% on those appliances' costs.
Phantom Power
Devices in standby mode still consume power. TVs, computers, chargers, and appliances with displays can draw 5-20W even when "off". Use power strips and turn them off completely to save $100-200/year.
Load Management
Avoid running multiple high-power appliances simultaneously. Stagger usage of dryer, oven, AC, and EV charger to reduce peak demand charges and improve efficiency. Some utilities charge extra for high peak demand.