NAME: _______________________________________ DATE: _____________
CLASS: ______________
HOME ENERGY AUDIT: ENERGY EFFICIENCY WORKSHEET
Calculating Lifecycle CostsHow much will an appliance
cost to buy and use over a lifetime?
|
purchase price |
+ |
(annual energy cost x estimated lifetime x discount factor) |
= |
lifecycle cost |
|
APPLIANCE |
ESTIMATED LIFETIME |
DISCOUNT FACTOR |
water heater |
13 |
.83 |
refrigerators and freezers |
20 |
.76 |
room air conditioner |
15 |
.81 |
dishwasher |
12 |
.84 |
clothes washer |
18 |
.78 |
Calculating Payback PeriodHow long will it take to
recover the extra money you spend for a more efficient appliance?
|
purchase price of more expensive model |
- |
purchase price of less expensive model |
= |
difference in purchase price |
|
higher yearly operating cost |
- |
lower annual operating cost |
= |
difference in annual operating cost |
difference in purchase price / difference in
annual operating cost = payback period
|
Example: You are shopping for a refrigerator. There
are two models. One casts $100 more than the other but saves
$25 per year in electricity costs. Which refigerator should you
buy?
|
|
$1000 |
purchase price of more expensive model |
|
- |
$900 |
purchase price of less expensive model |
|
= |
$100 |
difference in purchase price |
$100 / $25 savings
in electricity costs/year = 4 years
It would take 4 years to realize the savings. However, since
the payback period is only 4 years and your refrigerator will
last much longer than that, you will save money over the life
of the rerigerator and conserve natural resources.
Problems:
You would like to buy a new refrigerator and are looking
at two different models.
- If model A uses 700 kWh/year, how much is the yearly operating
cost (based on a cost of $.089 per kWh)?
- What is the lifecycle cost of model A if it cost $789?
- If model B uses 900 kWh/year, how much is the yearly operating
cost (based on a cost of $.089 per kWh)?
- What is the Lifecycle cost of Model B?
- If model A costs $789 to buy and model B costs only $700,
what is the payback period?
|