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About Wattage Calculator
What is wattage in electricity?
Wattage is a measure of power, quantifying the rate at which energy is transferred, and is named after the engineer James Watt. Essentially, when one ampere of current passes through one volt of potential difference, the energy transfer rate is measured as one watt. Watts are the basic unit for measuring power in electrical systems, much like speed is measured in miles-per-hour in the physical world. They indicate how fast electrical energy is flowing. One watt equals 3.4 BTUs per hour or one joule per second in metric terms.
For instance, a 60-watt lightbulb uses 60 watts of power per hour. A person working all day generates about 75 watts, while an average car might use 100,000 watts. The Vermont Yankee nuclear plant produces 650 megawatts (650,000,000 watts), whereas a small petrol generator can produce around 2,000 watts. Power ratings on appliances show how quickly they consume energy.
On your electricity bill, usage is recorded in kilowatt-hours (kWh). A kWh measures energy, not power. Energy is the capacity to perform work, like heating, lighting, or moving something. Since 1 kWh equals 1,000 watt-hours, running a 60-watt bulb for an hour uses 60 watt-hours or 0.06 kWh. Thus, it takes 0.06 kWh to power that bulb for an hour. Households are billed based on the kWh consumed, and utilities ensure they have enough power on hand to meet peak demand.
What is a volt?
Voltage measures the electric potential or pressure driving energy through a system. Measured in volts, it represents how quickly electrons flow in a circuit. In the US, power is delivered to homes at 120 volts and 240 volts, depending on the device. Most household items, such as light bulbs, TVs, and computers, run on 120 volts, while larger appliances, like air conditioners and ovens, require 240 volts. The term "volt" is derived from Alessandro Volta, an Italian physicist who built one of the first batteries in 1800.
What is an amp?
An ampere (or amp) measures electrical current. Defined by the SI, an amp is the amount of current that would cause a force of 2×10−7 newtons per metre of length between two parallel conductors one metre apart in a vacuum. This definition ties current flow to the electromagnetic force created between conductors.
What are ohms?
Wires and electrical devices naturally resist the flow of energy. This resistance is measured in ohms, named after German physicist Georg Simon Ohm. Electrical resistance slows the flow of electrons through a circuit, and copper or aluminium wiring in most homes adds some level of resistance.
How to calculate watts?
Calculating watts is straightforward if you know the current (amps) and voltage (volts) of a power source. You can measure these with a multimeter.
For DC circuits, the formula is simple:
W = A × V.
For example, if the voltage is 110 volts and the current is 5 amps, the power is 5 × 110 = 550 watts.
The formula for calculating wattage is:
W (joules per second) = V (joules per coulomb) × A (coulombs per second).
So, wattage is essentially the power used or generated per second. A 60-watt lightbulb consumes 60 joules of energy every second, determined by its voltage and current.
What is the difference between watts and volts?
Understanding the difference between watts and volts is key when working with electrical systems. Watts depend on both volts and amps, just as pressure and flow rate are connected in a water system. While voltage provides the "pressure," wattage shows how fast energy flows. This understanding is important when reading appliance ratings or working on electrical repairs.
