Water Heater System Test
Pensacola Energy, under the direction of Exelon Services Federal Group (ESFG), conducted a series of tests on three different water heater systems. We have posted the results below, to help you better decide which energy source best suits your family’s needs.
The three systems tested were an electric water heater, a natural gas water heater and a Rinnai natural gas tankless water heater.
Test 1: Monthly Operational Costs
In a comparison between the two traditional tank water heaters, the natural gas heater costs around 49% less to operate over the electric heater. The Rinnai tankless unit costs around 68% less to operate than the electric tank water heater and 37% less than the natural gas tank.
These percentages are based on the typical use of an average four-person household.
Test 2: Hot Water Delivery (in gallons)
The second test was to see how much hot water each system generates before running out. Beginning with an average out-going temperature of 135 degrees and ending with an average temperature of 80 degrees, the natural gas tank put out approximately 36% more hot water than the electric unit. For a better understanding, that is an extra 33.2 gallons of hot water for laundry, cleaning and bathing.
The Rinnai was not tested because it never runs out of hot water.
Test 3: Recovery Time (min:sec)
The last test was to see how much time it takes for the system to heat the water from 80 degrees to 135 degrees. According to the test, the natural gas water heater recovers around 64% faster than the electric unit — almost 40 minutes faster!
The Rinnai was not tested. Since it does not run out of hot water, it never needs to recover.
Summary of Results
| Water Heating System | Test #1 | Test #2 | Test #3 |
| Natural Gas Water Heater Rheem Model #21V4038 |
$18.11 | 95.5 | 21:35 |
| Electric Water Heater Rheem Model #81V40D |
$37.58 | 62.3 | 61:04 |
| Rinnai Natural Gas Tankless Water Heater |
$11.51 | Continuous Hot Water | Continuous Hot Water |
Testing Procedures
The testing procedures are derived in part from the “Test Procedures for Water Heaters” outlined by the Federal Register, Title 10 of the Code of Federal Regulations (CFR), Part 430. These regulations provide a standard for fair comparison between energy efficient, energy use and the annual operating cost of water heaters produced by different manufacturers.
You can review the testing procedures as defined by Exelon Services below. You will need Adobe Acrobat Reader to view the documents.