Tankless Water Heater Cost Comparisons NOTES AND ASSUMPTIONS
The consumer continues to ask for a broad range of Tankless Water Heater Cost Comparisons between the SEISCO tankless, storage-tank electric and gas water heaters. Often the consumer wants the comparisons to relate to the statements of the "Estimated Energy Cost" as shown on the storage-tank water heater labels.
1. The Label and the Real World Sometimes Differ
Its important that the consumer understand that labeling is required for certain appliances to conform to the Energy Policy and Conservation Act. Tests have been developed to estimate the energy efficiency and cost of operations for certain classes of water heaters. While the test protocol is intended to provide a method for a fair means of energy Tankless Water Heater Cost Comparisons, the parameters and protocol for these tests have forever been questioned or challenged. The problem in using such comparisons is that the testing has been established under specific laboratory conditions most of which can and do vary substantially in actual applications. Most important is the fact that some variations in actual application will effect the energy efficiency and operating costs of one class of water heater more than another. Very often the type heater and its location result in substantial increase in the air-conditioning or heating costs for the home. The following segments serve as examples.
- Unlike the laboratory test conditions, the BTU content for a therm (100,000 BTUs) of natural gas will vary from area to area. Areas whose natural gas has a lower BTU content than used in the laboratory testing will consume more gas thus cost more money heating water.
- The incoming water temperature, from which the DOE test calculations are being made, has been established at 57° F. In many parts of the U.S. one does not normally experience inlet water temperatures (delivered to the fixture) this cold year round.
- The ambient air temperature in which the water heater is tested is 68° F. Again, there are many Tankless Water Heater Installations, varying widely geographically, such as in a crawl space, basement, or attic where this temperature does not represent a genuine average ambient temperature.
- The storage-tank gas heater has to be vented. So long as the heater is placed outside the living area of the home, venting doesnt have a negative effect on other energy costs. In a very large percentage of the homes in the U.S., however, gas heaters are located in the living area and, as such, allow conditioned air, air that one has paid to heat or cool, to be forced out of the home. The conditioned air, that is lost, is replaced by infiltration of air drawn into the home from the outside, requiring additional heat or air-conditioning to heat or cool this outside replacement air. Furthermore, a fuel burning water heater will give off considerable heat to the inside of a home by virtue of the pilot and the hot vent. The vent itself reaches temperatures of 300° F above the inside temperature of the home. The effect of these conditions adds to the heating or air-conditioning cost. These costs are not added or even estimated in the energy label on a gas fired water heater. Imagine putting a 3" hole in your roof, and periodically heating a six-foot pipe to 375° F for the 2.5-3 hours per day your water heater is heating, in use or recovery. This hole in the roof is approximately equivalent to a 12" window left open one half inch 24 hours a day, 365 days a year.
2. Additional Energy Cost Estimates and Issues
The Energy Conservation Department of the California Energy Commission prepared a paper on gas water-heating costs. They developed a spreadsheet program for estimating the operating costs for gas storage-tank water heaters located outside the home and not in a conditioned space. The program assumes a household using 64.5 gallons of hot water daily, (DOE daily estimated hot water usage per household). With natural gas cost currently at $1.20 per therm of gas, the estimated operating costs for a 50-gallon gas tank heater is over $400 per year.
Of course, households are made-up of different size families that use various amounts of hot water. The amount of hot water used impacts the energy cost per household. Average hot water consumptions for various size households, according to Federal Agencies, are as follows:
1 person = 34 to 45 gallons/day
2 people = 43 to 58 gallons/day
4 people = 75 to 87 gallons/day
6 people = 105 to 122 gallons/day
3. SEISCO Has No Hidden Costs!
In reality, depending upon the climate and water temperatures, actual water heating costs for a 50-gallon gas heater could be less than $350 or more than $400 per year, even without including the impact of vent and stack loss on space heating and air-conditioning. Conservative calculations for the additional cost related to the loss of conditioned air to exceed an additional $100 per year.
The energy efficiency (AFUE), as the consumer understands the term, for most commonly installed electric storage-tank heaters is approximately 88%. The same efficiency for a comparable standard gas fired water heater is 54%. The efficiency for a SEISCO "flow-through" water heating system is over 99%. In 1997, a study was done by an independent consulting firm in College Station, Texas to compare the operating costs of a new 40gallon storage-tank electric water heater against the SEISCO. The test was done in January of l997. The results of this winter test indicated a monthly cost for heating water with the SEISCO, in this city during the month of January, to be less than $15.00 and a 26% savings over the 40 gal. electric storage tank water heater.
Gas water heaters become less efficient with use, particularly in areas of
hard water. Scale builds up on the walls of the tanks and mineral deposits collect at the bottom of the tank, both acting as insulation, reducing the efficiency for the transfer of heat from the burner to the water.
4. SEISCO Allows You To Save Energy and Water TOO!
Studies have indicated a normal household will draw varying amounts of hot water, turning the faucet off and on over 40 times daily. The normal flow rate from a faucet drawing hot water is estimated at 1.50 gallons per minute. There are obviously times and uses, such as the washing machine, when this draw is higher. At this nominal flow rate, assuming a wait for the hot water of an average of only 20 seconds, one half a (1/2) gallon of water is wasted. The total hot water wasted daily for 40 such draws would be at least 20 gallons. A great many households people experience much longer waits, and therefore more hot water is wasted, particularly in the winter.
It has been determined by independent sources that an average home will waste approximately 10,000 gallons of water per year running it down the drain waiting for hot water. Keep in mind that the water you draw out of the hot water faucet was originally delivered from the water heater. At one time this same water had been heated only to later cool down in a long run of pipes. By locating the SEISCO central to the major points of use, the estimated reduction in wasted hot water is 40% being 4,000 gallons per year and almost 11 gallons per day. The cost to heat this 4,000 gallons of water from 65° F. to 135° F., in an electric storage-tank heater (88% efficient) at $.084/kWh, is $65.00. The savings which are estimated in the following comparisons between the estimated cost of various types of water heaters includes an estimate of only 10 gallons saved as a result of ones ability to locate the SEISCO central to the major points of hot water usage.
5. Assumptions to Tankless Water Heater Cost Comparisons Tables
The following tables 1-3 are intended to represent a fair comparison for the estimate of the cost of heating water through the use of a SEISCO, a 50-gallon electric, a 50-gallon natural gas and 50-gallon LPG storage-tank heaters. The assumptions are as follows:
- The yearly average temperature for the incoming water is 65° F.
- The hot water temperature is set for the SEISCO at 120° F continuous.
- The storage-tank heaters have a capacity of 50 gallons.
- The storage-tank heaters are set at 135° F, where the majority of users set them.
- Utility costs are based on $0.084/kWh, $1.10/therm Nat. Gas and $1.60 gal. for LPG.
- A calculation of a conservative estimate of the impact stack, vent losses as well as combustion air requirements to additional heating and air conditioning costs (additional heating or cooling costs: A.H.C.) resulting from locating a gas storage-tank heater within the homes conditioned air space (basement).
- The hot water consumed daily is shown:
- Initially at 64 gal. for each.
- 55 gal. for the SEISCO reflecting the 10 gallons per day estimated hot water savings that can be obtained from the ability to locate the SEISCO within the living space central (equal-distant) to the major points of use.
- Then at 55 gal. daily for each, demonstrating that the reduction in gallons of use does not provide the same percentage savings for a storage-tank gas water heater(.54 eff.) as it does for electric (.88 eff.). The reason is simply the inherently higher standby losses for the gas heater irrespective of volume of hot water consumption.
