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

Determine Savings

Determine the Pay Back Period

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