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Sunday, 26 May 2013





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Energy-efficient practices will help reduce electricity bills

N.W.K. Jayatissa

With the massive electricity tariff which comes into effect this month, consumers are struggling to reduce electricity consumption.

There are limited options for cutting consumption because lifestyles cannot be changed overnight. However, enjoying sophisticated electrical appliances with power supply at subsidised rates is now over and the true cost has to be met by consumers.

Energy consultant and senior lecturer of the Department of Physics of the University of Kelaniya, N.W.K. Jayatissa said that consumers can reduce electricity bills by minimising waste and adopting energy- efficient practices.

Jayatissa is an energy consultant in Sri Lanka and New Zealand.

Following are excerpts of an interview with Sunday Observer Business.

Sri Lanka is among low electric power consuming countries with a per capita power consumption (KWh per capita) at 449 in 2010. However, with increasing per capita income and changing lifestyles, energy consumption is increasing. For instance in 2000, our per capita power consumption was 290 Kwh. Sri Lanka can yet save energy by introducing energy- efficient practices.

"In energy management we can consider three sectors; households, industries and commercial establishments. I will focus on the household sector. In households, energy consumption depends on various factors such as number of members in the family and of course lifestyles."

Management of energy in households should be initiated at the designing stage, before the construction of the house. Orientation of the house to make maximum use of daylight, ventilation, thermal resistance of the material used for walls and the roof are some of them. There are scientific methods to minimise energy use considering these factors.

However, in Sri Lanka we still do not observe them. In developed countries there is an energy rating system for houses and it is an important aspect in the pricing of houses.

If we are to consider saving energy in our homes, we need to have an idea of what share of our energy bill is being used for lighting, cooking and heating. According to recent research conducted by the students of the Department of Physics of the University of Kelaniya, 35-40 percent or the highest share of our electricity bill is for the refrigerator while around 20 percent is for lighting, around 25 percent for ironing and the TV and the rest for other purposes. Therefore, we should find out the energy killers in our households and introduce more energy-efficient practices.


Old refrigerators that are in use today are real energy killers. New technology has been developed and the latest refrigerators have more energy-efficient compressors and cooling methods.

Therefore, replacing your generations-old refrigerators with new ones may help you cut the electricity bill. New refrigerators have energy ratings that give an idea of their energy efficiency.

The size or the storage capacity of your refrigerator should depend on the number of people in the house and consumption pattern. In most cases, refrigerators are large and oversized and underserve the purpose for which they are meant.

Energy consumption of a refrigerator increases with the increase in frequency of opening it. If there is lot of space or air in the refrigerator cool air comes out every time you open it and more energy is needed to re-cool it.

Therefore, you should minimise empty space by packing stuff as much as possible in the fridge. You can store things such as water bottles to fill the space. If you can store the stuff in an orderly manner in your fridge and pre-decide what you want to pick before opening the fridge you can minimise energy waste.

Hot stuff should not be put into fridge until it reaches room temperature. Clean the door beadings and coils of your refrigerator frequently. Keep the fridge in a place where there is ventilation and no direct sunlight, which may also help to reduce energy waste.


Energy efficient houses can be designed to get the maximum benefit from daylight. There are standard architectural designs for this. You can save energy by selecting suitable bulbs for different purposes in your house.

The bulbs should be selected based on Lumens and Watts. Watts measure the amount of energy used by bulbs and the Lumens is the measure of brightness provided by a bulb. The more the Lumens, the brighter the bulb. Selection of the bulb should be also be based on the lux level of the light that is needed for the purpose.

There are recommended lux levels and it may vary from country to country.

Table 1 gives a guideline. Lux is the light density so you have to multiply it with room area to find out the required Lumens.

Table 2 gives the relationship among candescent, CFL and LED bulb wattage levels and lumens.

You should look at lumens of the bulb not the wattage when you purchase a bulb. CFL and LED bulbs are energy- efficient options that can save a significant amount from the electricity bill. A single switch for a single bulb and dimmers can be also used to save energy in the lighting of houses.

Rice cooker

The rice cooker is another appliance that consumes more electricity. Since gas is cheaper than electricity in Sri Lanka, you can reduce 7-8 units of electricity consumption and total energy cost by shifting to gas. This is an option for consumers in the margin of 90 units who want to keep consumption below 90 units. Small pedestal fans are more energy efficient compared to ceiling fans. The fan should be selected considering the size of the room. If the fans are wobbling, energy waste is high.

The size of the washing machine should be decided considering the number persons in the family. Large oversized washing machines waste energy. If you wash a full load you can save energy, because even for a half a load the washing cycle is the same. Overloading leads to a longer drying time and energy waste.


Electricity can be saved if you iron clothes in bulk. May be what you need for the whole week, at once. Loss can be minimised if you start ironing with heavy clothes and end with soft clothes. If you hang the clothes after washing, the ironing time could be reduced.

The solar-powered hot water system is the cheapest option. Water heating consumes a significant amount of electricity and this is one of the convenient alternative energy use options at household level.

Air conditioning

In Sri Lanka we do yet not use a scientific approach by calculating the cooling load in the installation of AC machines and therefore it is one of the main energy wasters.

There are several important factors that should be considered. External heat that comes into the room depends on solar heat, the direction of sunlight, thermal resistance of roof and walls, thickness of the walls while the internal load depends on the number of people and appliances working in the room. The cooling load is calculated using all these factors.

The size of the machine is determined by adding 10 percent to the cooling load. Other factors such as direction and height of installation of the AC machine, distance between machine and splitter, and insulation of the room have to be considered.

Electricity consumption of a correctly installed AC machine is a little more than the amount consumed by a fan. Most of the AC machines installed by vendors are oversized and they only attempt to sell a machine. Such machines always work at an inefficient range and waste energy.

People's knowledge on energy-efficient methods and the correct use of electrical appliances is extremely low in Sri Lanka.

They make decisions based on commercial advertising which gives wrong information. The Government too has a responsibility to educate people on methods of efficient energy use.

Most of the electrical appliances are no longer luxuries and they are essential household equipment and therefore even with the huge rate increase, people cannot change their lifestyles overnight. The co-operation of all family members is essential to implement energy saving practices.


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