Lesson 14 — Activity 3:

Examining Energy

Efficiency



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You know that in energy transformations, energy is not created nor destroyed. Instead, it is transformed or changed into some other form so that it can do work. In this activity, you will learn more about how to be energy efficient and make choices that conserve energy.

You know that in every energy transformation, not all the energy available is transformed to the use you have in mind. Some energy is lost as heat or to friction or incomplete combustion. This loss is sometimes referred to as energy dissipation. For these reasons, you need to know that you are making responsible choices when you use energy. Wasting energy wastes money and harms the environment.

So, how can you tell whether the machine or device you are using is the best choice for a particular job? As you learned with machines, you can calculate the efficiency of various devices. This activity teaches you how to calculate the power rating of various machines to see how much energy they use.

 

The mathematical equation looks like this:

Power (P) = Current (I) x Voltage (V)

Using symbols, the equation looks like this:

P = I x V

Note: The current (I) is measured in amperes (amps).


Note: SI means International System of Units.
Watts are the unit for measuring power.

 


 

Let's look at an example. What is the power of a 5 amp (I), 2 voltage (V) lamp?

P = I x V

P = 5 x 2
P = 10 W

The power of the lamp is 10 watts.


Let's take a look at another example to find out which lamp is the most energy efficient.

What is the power of a 5 amp (I), 12 voltage (V) lamp?

P = I x V

P = 5 x 12
P = 60 W

The power of the lamp is 60 watts.


Power refers to the rate at which a device converts energy. The more quickly the energy is converted, the more powerful the device. Therefore, the second lamp would be more energy efficient as the energy is converted more quickly!

 

Big or small, your household appliances and electronic devices consume a lot of energy. On average, they consume 20% of the total energy used in your home. The refrigerator is the biggest energy guzzler, followed by the freezer, the washing machine (if it uses hot water), the dryer, the dishwasher, and the stove. Smaller appliances can provide big savings in energy consumption. Therefore, when you have a choice of using one or the other, always choose to use the smaller appliance. Whether it is a microwave oven, a toaster oven, a crock pot, a tea kettle, a coffee maker, or an electric skillet, don’t be afraid to use them as often as you can.

 

In Canada, the EnerGuide system helps consumers determine whether the appliances they want to buy are energy efficient. Appliances must be sold with EnerGuide labels that show how much energy the appliance will use on average in a month or year. Consumers can use the information on these labels to compare the efficiency of various models.

 

Here is an example of a Canadian EnerGuide label for a 42" plasma TV.



The label shows that it will cost about $70 per year to use this TV (based on approximately five hours of viewing per day).

 



As well, always look for the Energy Star label when purchasing appliances. Energy Star tells you which appliances are the most energy efficient. Products that have the Energy Star label will help reduce your energy and operating costs by 30 to 50%. You’ll also be helping the environment. For a refrigerator, you can save upwards of $80 per year.

 

There are many ways that you can conserve energy in your home. Let's take a look at some of them below.

  1. Wear the right clothes: Dress for the temperature. Layering clothes and wearing wool helps keep you warm in winter and means you can turn your heater down.
  2. Shut doors and close curtains: Heating or cooling the whole house can be expensive. Where possible, shut doors to areas you are not using and only heat or cool the rooms you spend the most time in. 
  3. Set your thermostat: In winter heating can account for over 30% of your bill. Set your thermostat between 18 and 20 degrees Celcius. Every degree higher than 20 can add 10% to your heating bill. In summer, set your thermostat to 26 degrees Celcius or above.
  4. Turn heaters and coolers off when you don't need them: Turn off when you leave the room or go to bed. Make sure all your heating or cooling is turned off when you leave the house.
  5. Wash clothes using cold water: You can save around $115 per year by washing clothes in cold water. You can also save by making sure you select the shortest appropriate washing cycle and waiting until you have a full load.
  6. Run your fridge efficiently: Your fridge is always on, making it one of your most expensive appliances. Make sure the door seal is tight and free from gaps so cold air can't escape. An ideal fridge temperature is 4 or 5 degrees Celcius, and an ideal freezer temperature is -15 to -18 degrees Celsius.
  7. Save energy in the kitchen: Thaw frozen food in your fridge to reduce cooking time. When you are cooking, use the microwave when you can. It uses much less energy than an electric oven. If you use the stove, keep lids on your pots to reduce cooking time. Use the economy cycle on your dishwasher and only run it when it's full.
  8. Use energy-efficient light bulbs: Replace old incandescent and halogen light bulbs with energy-efficient bulbs. Energy-efficient bulbs save power and last longer.


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