Time = f(Energy,Power)

The Time calculator computes the time required (Δt) to consume an amount of energy (ΔE) at a constant power (P).

INSTRUCTIONS: Choose units and enter the following:

• (P) This is the constant power expended during the time.
• (ΔE) This is the change in time.

Time(Δt): The calculator returns the time in seconds.  However, this can be converted to compatible units via the pull-down menu.

The Math / Science

The formula for the change in energy due to power is:

          ΔE = P * Δt

where:

• P is the constant power expended during the time.
• Δt is the change in time.

Solving for time, we have the following formula:

        Δt = ΔE / P 

Power is the amount of energy consumed or produced over time.

• Power is a measurement of the energy used to move vehicles (automobiles, trucks, tractors, trains, boats and airplanes).
• Power is the measurement of energy consumed by a motor and transferred to the drive or wheels. 
• Power is the amount of electrical energy consumed or produced by a system over time such as the energy produced by a hydroelectric dam or energy consumed by an electrical motor.

Power Units

Power is most commonly measured in watts (W).  One watt is equal to one joule per second (1 W = 1 J / 1 s).  Power is also measured in horsepower (hp) where 1 horsepower equals 745.7 watts.  Power is also measured in heat energy transfer as BTUs per hour (BTU/h).

Power Calculators

• Power from Change in Energy over Time
• Power based on Force and Velocity
• P = ΔE / Δt
• ΔE = P * Δt
•  Δt = ΔE / P 
• Power Dissipated by Friction
• Power from Force, Distance and Time
• Power from Resistance and Current
• Power from Voltage and Resistance
• Power from Current and Voltage
• Power textbook chapter (Light and Matter)

Applications

1. How long would it take consume 1200 kilowatt hours of energy using a 400 Watt motor?