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.

Click here to open a text description comparing the two EnergyGuide Labels.

### 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

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:

- Yes
- 367 kWh
- $45

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:

- 1.33 years
- $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 CO_{2}, 21 lb of NO_{x}, 75 lb of SO_{2} and 1 lb of CO and particulate matter each and into the environment. See the individual’s power!