The Kenmore Power Miser 9 40-gallon gas water heater is estimated to use 250 therms of energy per year of operation, a high consumption figure compared to other water heaters at the time of its manufacture. It is not qualified as an Energy Star product by the Department of Energy.
The Department of Energy estimated that the 40-gallon version of Kenmore Power Miser 9 costs approximately $304 dollars to run based on the cost of natural gas per therm at the time it was manufactured. This is greater than approximately 75 percent of the water heaters available at the time. The gas water heater using the lowest amount of gas per year was estimated to cost only $273 dollars per year to run. Larger or smaller models of the Power Miser 9 water heater may use more or less energy than the 40-gallon model.
Despite its name, the Power Miser 9 uses few of the features found on more efficient gas water heaters as of 2015. Many modern high-efficiency gas and electric water heaters use heat pump technology to effectively transfer heat from the surrounding air to the water in the tank to save energy, only using full-power heating for high-demand situations, such as showers. Other gas heaters forgo a tank entirely and heat water on demand rather than heating a full tank of water all at once as the Power Miser 9 does.