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Calculate Cost of Lighting Usage in 5 Simple Steps

Calculate Cost of Lighting Usage in 5 Simple Steps

Don Chew |

If you are always wondering why your utility bills are high and thinks that lightings contribute to the major costs of your utility bill, this is the article for you.

Find out, quantify and calculate how much lightings costs you in 5 easy steps.

Power kW of Lighting

First, the Power (kW) of One Lamp

Usually the lamp has the wattage written on the lamp. For example, if your lamp is 18W, if converted to kW (18W divided by 1000) you would get 0.018kW.

Power kW of Lamp

Second, the Cost of a Unit for 1kWH

The cost for 1kWH means the cost for using 1kW within an hour.

You would find these values in your utility bill. As for our country in Malaysia, the cost of 1kWH differs based on a scaled monthly usage per month and also dependent whether you are a Residential user or a Commercial user. For simplicity, we shall use the highest unit rate in my example bill.

Based on my example here, we can take a value of RM0.571 for 1kWH.

TNB kWH Rate per Unit

Third, how many long in hours do you Switch-ON your lights Daily?

In my example, for a living area, most users switch on around 6 hours daily. We assume this usage would normally happen at night. Hence, with this, I would use 6 hours as the value.

Usage of Lamps in Hours and Days

Fourth, how many Days do you Switch-ON the lights within a Month?

If it is lit every day, I would use 30.5 days. Because there are some months of 30 days and some months of 31 days.

Fifth, lastly, what is the Quantity of Lights do you Switch ON?

Let’s say your place has 12 lights and we use 12 as the specific value.

With this, multiply all these numbers, 0.018kW X RM0.571 X 6 Hours A Day X 30.5 Days A Month X 12 Lamps, your Cost of Usage of these Lamps would costs you RM22.57.

Summary Cost of Usage


This cost calculation is suitable for all types of lamps or any other electrical appliances.

Hence, if you wish to reduce the cost of lamps usage, do switch on specifically for only when necessary and within a required amount of time.

If the usage, is unavoidable, do ensure your lamps are LED-based to ensure energy efficiency for the same amount of light output.