Replacement Gas Water Heaters

The life of a gas water heater will vary depending on care and maintenance of the unit and factors like mineral content of the water. On average, most water heaters will need to be replaced after 10 to 12 years. When replacing a water heater, remember that there are two costs to consider - the initial cost and the energy cost, which is a function of the water heater's efficiency.

Water Heater Efficiency Ratings

Water heater efficiency is expressed as an Energy Factor (EF), which is a decimal equivalent of a percent efficiency (.60 EF = 60% efficient). It compares the heat energy delivered to the water to the total energy consumption of the water heater. The higher the Energy Factor, the less it will cost to heat water.

New gas water heaters have Energy Factors ranging from .56 to as high as .67, and new technologies under development are expected to have Energy Factors of .80 or higher.

First Hour Rating

This rating indicates the amount of hot water the water heater can supply in the first hour of operation. It is a combined measurement of how much water is stored in the water heater and how quickly the water heater can heat cold water to the desired temperature. You can use this rating to select the appropriate size water heater and to compare hot water delivery capabilities of similar models.

Efficiency Improvements

High-efficiency gas water heaters have several features that reduce the cost of heating water.

  • The tank walls have higher levels of insulation, some as high as R-13.
  • Some high-efficiency models use an intermittent ignition to light the burner, replacing the constantly burning pilot light.
  • The heat exchanger efficiencies are improved, extracting more heat from the gas and letting less escape up the exhaust vent.
  • Some models feature sealed combustion burners and power venting for even greater efficiency.

Condensing Water Heaters

The newest type of gas water heater is called a condensing water heater. With a conventional gas water heater, a large portion of the heat from the burners escapes up the vent. A condensing water heater uses a much larger heat exchange surface that extracts much more of the heat before venting the exhaust.

Insulating the Tank

In the past, water heater insulation blankets were widely recommended. Older water heaters had much less internal insulation than current models and the added insulation helped to reduce "standby losses" and overall water heating costs. Today's water heater tanks are built with much higher levels of internal insulation, so an external insulation blanket is much less important. If you do decide to install an external blanket, be careful not to block the airflow to the combustion chamber (usually at the bottom) or the vent at the top.

What To Look For

The Federal Trade Commission requires all storage type water heaters to be labeled with an "EnergyGuide" label, which shows the estimated annual operating cost for that water heater and how it compares with other comparable models.

The Air Conditioning, Heating and Refrigeration Institute (AHRI) sponsors an efficiency certification program that verifies manufacturers' equipment efficiency ratings according to a standard test method. AHRI maintains an online directory that lists the manufacturer, model number and Energy Factor of all tested water heaters.

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