Payback time!
Which has the shortest payback time?
Which will save the most money in 5
years?
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Payback time
Each insulation method has a different
cost and saving, so we calculate ‘payback
time’ for a direct comparison.
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Loft insulation
A thick layer of insulation of the loft floor.
It works because it’s a poor conductor and traps air,
stopping convection.
Cost - £450
Saves - £150 every year.
What is the payback time?
How much saved after 5 years?
3
Draught excluders
Brushes and seals on doors.
Prevents warm air escaping
from the home via convection.
Cost - £30
Saves - £20 every year.
What is the payback time?
How much saved after 5 years?
4
Payback time
Use this equation to determine the
payback time of each method.
Then decide which method you would
decide to do first.
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Application
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6.
Explain what is meant by the term ‘payback time’.
The double-glazing for a house costs £3,000 but saves £150 per year in
fuel costs. What is its payback time?
The cavity wall insulation in a house costs £6000 to install. It has a
payback time of 15 years. How much money does the insulation save
each year in fuel costs?
A draught excluder has a payback time of 2 years and saves £20 in fuel
costs per year. How much did the draught excluder cost?
A family purchase loft insulation costing £3000 which saves them £250
per year in fuel costs. The family plan to remain in this house for another
10 years. Was this a worthwhile investment? Explain your answer.
A family spend £4000 on double glazing which saves them £250 per year
in fuel costs. How long will the family have to remain in this house to
recoup their investment
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Cost effectiveness
If savings are bigger than initial and
running costs then the method is cost
effective and worth doing.
All costs need to be accounted for such
as installing costs, interest on loan to
buy equipment etc…
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