Payback Times (GCSE Physics)


Uploaded by freeeschool on 04.09.2012

Transcript:
GCSE Physics Ð Payback Times
Hello and welcome! In this video, we are going to look at Payback Times. ThatÕs related
to energy efficiency of homes and buildings and we are going to look at how payback times
can be calculated and savings that can be made by using various methods for insulating
and saving energy in the home.
To start off, hereÕs just a diagram of what a house might look like. There are various
ways that you can save energy in this home. The first type of example that you might have
is for example, cavity wall insulation. This is when there is an extra layer put on the
surface of the wall and then between the extra layers, there is some insulating material
placed in there. We can have loft insulation which is like an insulating layer thatÕs
put into the loft just to prevent heat. This is performed through the ceiling. Double glazing
or double layering windows and something simple like draft excluders. There are just some
simple ways to reduce the amount of energy that is lost from you home and that can lead
to saving money.
How much does it cost to put some of these things in and what are the savings? This is
a question that we often have to think about if we are going insulate homes. What we have
enough to consider is what we call Payback Times.
Just to give an example of what that means, letÕs go through a scenario here. Imagine
that the cost of installing double glazing is £5,000 and as a result of installing double
glazing, you are going to save £500 per year on your energy bills. So every year, you save
£500.
How long will it be before you have saved that £5,000 or you have paid back that £5,000?
Very simply, in the first year, youÕll save £500. In the second year, youÕll save in
total of £1,000 and in the third year, £1,500 and so on. You could carry all the way up
to when you reach £5,000 and that would actually be in 10 years. So in 10 years, you would
have saved your £5,000. We say that the payback time for installing double glazing for this
example is 10 years.
Now, letÕs have a look at a few more examples and do a bit of practice on this. Here are
some various methods of insulating your home or actually saving energy in the home. The
first one is loft insulation. If you are to use loft insulation or install loft installation,
how much would that cost or save you? How long is the payback time?
LetÕs have a look. The cost is £200. We save £40 every year. So after the first year,
for example, first year, we say £40, the second year is £80 and the third year is
£120. The fourth year is £160 and the fifth year is your £200. We have saved £200 over
five years and so the payback time is five years.
The second example, we got to do this in a much more simple way, we donÕt have to do
this through this way is we can just divide the total cost by the savings per year. For
example No. 2, installing an energy-efficient washing machine will cost us £650. It saves
us £50 per year. We just divide £650 by £50 and that gives us an answer of 13 and
so the payback time for installing an energy-efficient washing machine is 13 years.
Low energy light bulbs cost is £100 divided by £20 and thatÕs a payback time of five
years.
If you change all your energy, all your light bulbs into lower energy light bulbs, you will
save £20 per year as for this example. Then you will pay that money back in five years
time.
ThatÕs an overview of Payback Times and how to calculate it and hopefully, you got a clear
idea of how to do that.
[end of audio Ð 04:22] GCSE Physics Ð Payback Times
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