Calculating Electric Consumption Power: A Step-by-Step Guide

Want to lower your electricity bill and find the right devices for your home? Look no further - here is our comprehensive guide on calculating power consumption. Learn all you need to know with us!


1. What is power?

Power, symbolized by P (abbreviation for Potestas), is the measure of work done in a unit of time. It can be classified into mechanical power and consumption power:

  • Mechanical power is used in uniform motion and rotational motion.
  • Consumption power is the energy of electrical energy transformed into useful energy.

What is power?

In practical terms, power indicates the amount of energy consumed by electrical appliances in a unit of time.

2. How to calculate power consumption

Most manufacturers specify the operating power of electrical appliances. This information allows you to easily calculate the amount of electricity consumed in a month, helping you plan your electricity usage according to your family’s budget.

The formula for calculating power consumption is as follows:

A = Amount of electricity consumed (KWh)
P = Consumption power (KW)
t = Time of use (h)

Conversion to W:

  • 1KW = 1000W
  • 1MW = 1,000,000W


Let’s say an air conditioner has a power of 120W (0.12KW) and operates for one day (24h). The amount of electricity consumed by the unit would be 0.12 x 24 = 2.88 (KWh).

Power consumption of devices

In addition, if the product’s energy label mentions energy consumption, you can also calculate the amount of electricity consumed by the device in one day.


Let’s say the energy consumption of a refrigerator is 381 KWh/year. The amount of electricity consumed by the refrigerator in one day would be 381 (KWh) / 365 (days) ≈ 1.04 (KWh).

3. How to calculate 3-phase power

What is 3-phase power?

3-phase power is a high-power and high-energy consumption current. The voltage (V) at each location in the world may vary. In Vietnam, the standard voltage for 3-phase power is 360V.

This type of current is more costly compared to single-phase power and is typically used for industrial machinery such as car washers, industrial sewing machines, and industrial washing machines.

What is 3-phase power?

Formula for calculating 3-phase power

Each type of industrial machine has an inspection label and electrical consumption parameters on the machine body. You can calculate 3-phase power in 2 ways:

Method 1:

A = U x I x t

Method 2:

A = U x I x t x Cosφ

3-phase power meter

This article has provided you with a detailed and accurate method for calculating power consumption. If you have any questions, please leave a comment below, and we will be happy to answer them!