EGEE 102
Energy Conservation and Environmental Protection

Life Cycle Analysis

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Let’s use the Energy Guide to perform a life-cycle analysis to help choose a water heater. Different models of water heaters with the same capacity can vary dramatically in the amount of electricity they use.

Text description of the Life Cycle Analysis activity.

Instructions: Use the two EnergyGuide Labels for the different water heaters, to answer questions 1-8.

EnergyGuide Label for the $388.00 Water Heater
Sold for $380.00
EnergyGuide Label for the $350.00 Water Heater
Sold for $335.00

Compare the Two EnergyGuide Labels

 

Water Heater #1:

  • Water heater: Electric
  • Capacity (first hour rating): 58 gallons
  • This model uses 4622 kwh/year
  • Energy use range of all similar models (kwh/year): 4624 (uses least energy) - 5109 (uses most energy)
  • This model's estimated yearly operating cost is $388
  • Based on a 1994 U.S. Government national average cost of $0.0841 per kWh for electricity. Your actual operating cost will vary depending on your local utility rates and your use of the product.
  • Sold for $380

 

Water Heater #2:

  • Water heater: Electric
  • Capacity (first hour rating): 58 gallons
  • This model uses 4989kwh/year
  • Energy use range of all similar models (kwh/year): 4624 (uses least energy) - 5109 (uses most energy)
  • This model's estimated yearly operating cost is $419
  • Based on a 1994 U.S. Government national average cost of $0.0841 per kWh for electricity. Your actual operating cost will vary depending on your local utility rates and your use of the product.
  • Sold for $335
Compare the Two Models

1) Are the sizes and features similar for both water heaters?

a. Yes

b. No

 

2) Calculate the annual energy savings of the more energy efficient model (hint: the difference between the annual energy consumption values).

a. 136 kWh

b. 276 kWh

c. 326 kWh

d. 367 kWh

 

3) Calculate the price difference between the two models.

a. $25

b. $35

c. $45

d. $55

 

 

Answers:

  1. Yes
  2. 367 kWh
  3. $45
Determine Savings

Next assuming that the cost of electricity in the State College area is $0.092/kWh, and the life expectancy is 13 years, respond to the following questions about the EnergyGuide Labels.

 

4) Calculate the annual monetary savings on energy for the model with lower energy consumption (Hint: annual energy savings x cost of electricity).

a. $33.76

b. $85.88

c. $165.15

d. $337.60

 

5) Calculate the amount of energy saved over the lifetime of the appliance (Hint: annual energy savings x life expectancy in years).

a. 4287 kWh

b. 4388 kWh

c. 46810 kWh

d. 4771 kWh

 

6) Calculate the cost of energy savings over the lifetime of the appliance (Hint: annual monetary savings x life expectancy in years).

a. $348.96

b. $386.48

c. $438.93

d. $496.84

 

 

Answers:

  1. $33.76
  2. 4771 kWh
  3. $438.93
Determine the Payback Period

7) Calculate the Pay Back Period or years to recover the additional investment (Hint: how many years will it take to get back the price difference between the two models based solely on your annual monetary saving?

a. 1 year

b. 1.33 years

c. 1.5 years

d. 2 years

 

8) Calculate the total monetary benefit for choosing the more energy efficient model (Hint: monetary savings over the appliance's lifetime minus the price difference of two models).

a. $343.76

b. $393.96

c. $496.34

d. $634.76

 

 

Answers:

  1. 1.33 years
  2. $393.96

Still trying to figure out the payback period? The price difference between the two models was $45, and your annual monetary savings was $33.76. So after one year, you got back $33.76 out of the $45 extra you spent on the superior model. How much longer would it take you to get back the remaining $11.24? Since $11.24 is about a third of $33.76, it would take you about a third of a year. Thus your payback period is 1.33 years.

 

Obviously it pays to buy an energy-efficient water heater by saving $393.96. It also helps the environment by not using 4,771 kWh of electrical energy and thereby not emitting 9,652 lb of CO2, 21 lb of NOx, 75 lb of SO2 and 1 lb of CO and particulate matter each and into the environment. See the individual’s power!

A happy home owner with his new efficient water heater.
A happy homeowner with his new efficient water heater.