Water softeners virtually eliminate energy-wasting, service life-shortening scale accumulation on gas and electric water heaters, according to a new study by Battelle Memorial Institute on "Benefits of removal of water hardness (calcium and magnesium ions) from a water supply." Testing electric water heaters over an equivalent 15 months of service found 64 times more scaling on unsoftened water than softened water (14 grams/year softened versus 907 g/yr for unsoftened). For gas water heaters, the scale reduction was even more dramatic. Over more than two years' equivalent service, heaters fed with unsoftened water accumulated 74 time the amount of scaling as those fed softened water (7 g/yr for softened versus 528 for unsoftened). Instantaneous gas heaters fed unsoftened water declined in thermal efficiency from 80 to 72 and, even when delimed, only recovered 62% of the lost efficiency. The thermal efficiency of all water heaters using softened water was unimpaired.
For gas storage and instantaneous water heaters, the use of a water softener to eliminate or minimize the scale forming compounds in water will result in the efficiency of the water heater remaining constant over the life of the unit. In contrast, gas storage and instantaneous water heaters using unsoftened water had a noticeable decrease in efficiency over the testing period resulting in higher natural gas use.
The increase in total energy consumption (as a result of a reduction in heat transfer efficiency) is related to hardness: higher water hardness will lead to greater energy consumption without the use of water softener, and consequently greater energy costs."
The report calculates the percentage of lifecycle energy cost savings using softeners ranging from 3.1% for "moderately hard" water with 5 grains hardness per gallon to 6.6% for "hard" water with 10 grains hardness, 14.5% for "very hard" water with 20 grains hardness and 24.2% for water with 30 grains hardness.