Units

Units of Energy

• The basic unit of energy is the Joule (J).
• More specifically, 1 Joule of energy is equal to 1 Newton meter.
• Kilowatt-hour (kWh) is a unit commonly used for energy consumption; 1 kWh equals 3.6 million Joules.

Units of Power

• The basic unit of power is the Watt (W).
• 1 Watt is equivalent to 1 Joule of energy transferred per second (J/s).
• Kilowatts (kW) is a typical household level measurement, with most domestic electrical items rated between 1KW and 3KW.
• MegaWatts (MW) are used for large power stations; for instance, large power stations might be rated in hundreds of MW.

Units of Work Done

• Work done is also measured in Joules (J).
• When a force of one Newton moves an object a distance of one meter, the work done is 1 Joule.

Conversion Factors

• Power and energy have a direct relationship and can be converted using time: Energy = Power x Time.
• To change from kWh to J, multiply by 3,600,000. To change from J to kWh, divide by 3,600,000.
• Remember that when you’re dealing with units, it’s crucial to keep track of your conversions to make sure your final answer makes sense.

Heat units

• The amount of heat energy required to increase the temperature of one kilogram of water by one degree Celsius is called one calorie.
• More usually, the unit of heat energy in the SI system is the joule.

Units of Force

• The metric unit of force is the Newton (N).