In many instances, the same purpose can be achieved using various different
appliances. In order to get illumination we can use filament bulbs, fluorescent
light tubes or CFL lights (compact fluorescent lights). Choosing a more efficient
appliance helps us to save energy. A few different types of bulbs giving the same
illumination, their power output and life times are given in Table
According to Table, it is advantageous to use LED bulbs as light sources.
However, the use of good quality LED bulbs is limited due to their high initial cost.
Similarly, the efficiencies of cookers used to prepare food are different from one to
another due to varying amounts of heat wastage. Old cookers that use heating coils
are the lowest in efficiency. Emersion heater is highly efficient for heating water.
The reason is that, all the heat generated in the heater is transferred to water when
using it. Heaters which contains hot plates such as rice cooker is more efficient
because heat loss is less from them. Although microwave ovens cannot be used
to cook all types of food, they are very efficient since they produce heat inside the
food items. In addition to these, induction cookers with high efficiencies are now
available in the market. In these devices, the variable magnetic field emitted by the
cooker generates heat only at the bottom of the cooking utensil.
