kW and kWh are very different measures of power usage and it can be very confusing determining the difference. Even energy professionals sometimes struggle to understand the differences, but this article will explain all. kW is a measure of power and kWh is a measure of energy. Power and energy are two very different things, and understanding this relationship is the first important step to take.
What is power?
Power is the rate at which energy is generated or used, and this is measured in kW. Strictly speaking, energy is never created; it is merely changed from one form to another, but for the purposes of this article, power in kW relates to the rate at which energy is used.
What is energy?
Energy is a measure of how much fuel, which can be turned into power, is stored within an item. It is also a measure or fuel used over a specific period of time. The kWh is the measure of the amount of kW used in the period of one hour.
So how do power and energy relate?
Power and energy have a relationship that is basically equivalent to distance and speed. The measure of energy (kWh) is equivalent to the distance travelled over a period of time; it is the amount of fuel used over the period of one hour. The measure of power (kW) is instead equivalent to speed; it is the value of usage at one specific moment in time.
Why have two measures?
Both distance and speed are useful measures for different circumstances and likewise power and energy are both necessary measures for different contexts. At some points it is useful to talk about the rate at which power is being used at a point in time (kW), and at other times it is useful to consider the measure of energy over a period of time instead (kWh).
Which figure should I use?
Determining which figure to use is often difficult when you are talking about electricity usage. The majority of inexperienced people will tend to use kWh far more readily as a measure, but more experienced people will generally find kW a more useful measure. Average power is typically measured in kW and this is a very useful figure for calculating the average energy usage of a home. In many ways kW is a more useful measure, but both figures have their uses and your electricity suppliers will quote both too.
Calculating an average
Your electricity supplier will generally be responsible for measuring and assessing your power usage in the home. Understanding the averages and the usage of power and energy in your home can be very helpful, however, and electrical testing can provide some enlightening information about inefficiencies that are costing you money.
Your electricity meter is the most accurate measure of power usage in the home and you can calculate your average by recording a figure at the same time each day and calculating the difference over a number of days. With this information you will be able to budget better and will be able to recognise inefficiencies that need to be fixed.