Hot Water – On Demand
In my quest for achieving not merely an energy efficient home… but instead, reducing our energy consumption, I have taken the next big step in trying to get my combined monthly utility bills below $50. (Read more about these efforts in the ‘Energy Audit’ section of my web site at www.oxbowinspections.com). This is something simple that everyone should do: Install an ‘on-demand’ hot water heater. Most American households spend between $10-$25 per/month in merely heating hot water. Virtually all American homes have a hot water heater. Typically, they come in sizes of between 40 to 65 gallons. We spend money on utilities (energy) to keep all that water hot… all of the time! Why? This would be akin to putting a full tea kettle on the stove at medium heat, and then leaving it on day and night, forever, just in case we might want to make a cup of tea. This is insane, and of course, none of us would ever do such a thing. But most of us are in fact doing just such a thing. We waste energy 24 hours a day 7 days a week 365 days a year just trying to keep 40+ gallons of water hot all of the time. This, too, is insane.
The solution? Install a “tankless”, or “on-demand” hot water system. This is pretty new technology for North America. I have been inspecting homes for years, and have yet to see one of these amazing units in operation in any of the homes I inspect. However, tankless systems have been used in Europe and in Japan for decades. The American concept of having 40 to 60 gallons of hot water ready and hot at all times… just sitting around and consuming energy 24 hours a day just to stay hot in case it is needed, is a totally foreign concept to both the Japanese and the Europeans. It made no sense to me either as to why I should spend money to heat all that water, and spend even more money to keep it heated all of the time… just in case I might want some hot water for a few minutes during the course of a day. So, I purchased a new electric tankless on-demand unit for my home from a German company called Stiebel. It took about 4 hours to install. It sits on the wall and is not much bigger than a shoe box. The cost was the same as the cost for another traditional, 50 gallon water heater. So, I removed the 50 gallon water heater tank I was using… and now I have all that space freed up for use as a closet that before, had only room for 50 gallons of hot water. I started saving energy ($$money$$) immediately. My electric usage went from 82.8 kilowatt hours in July 2007, to only 54.6 kilowatt hours in July 2008. This tankless wonder immediately cut my electric bill by more than 30%. It will pay for itself in less than 2 years.
There is no requirement for hot water while I am away from home, so my new water heater heats no water at all, resulting in immediate energy savings. When I am home, this little wonder only heats water when I turn on the hot valve on the sink etc… There is a considerable energy savings as there is no longer a huge hot water tank working 24 hours a day just to keep a reservoir of hot water. The hot water output varies with different models, ranging from the very small units designed for just one sink or one dishwasher, to the much larger units designed for the entire house. Mine is a ‘whole house’ unit, and it still is not much bigger than a shoe box. Fuel savings (electric/propane/natural gas) from my any on-demand system is estimated to be between 30% to 50% per year (they can be 8% – 14% more energy efficient for homes that use a lot of hot water (a lot=86 gallons or more per day)). And, unlike my old water heater tank which could run out of hot water… the supply of hot water in my tankless system is endless, with flow rates high enough to run a bathtub, two sinks, and a dishwasher… all at the same time, with whisper quiet operation.
This type of system is not well suited to every American household. Homes with large families who use their hot water on and off all day long are generally not satisfied with the tankless systems. Using hot water continually throughout the day would negate any possible monetary savings realized by not having to heat a hot water tank. You need to evaluate your own needs and consumption habits before plunging into purchasing this type of system. Some people have found the need to add a small hot water tank to make their system viable for their use. RULE OF THUMB: Generally, if nobody is home for much of the day, and nobody is awake for most of the night, then there is simply no need to spend money on energy to keep a reservoir of hot water, and a tankless on-demand unit is the recipe for you. Most families in America would find this system ideally suited to their lifestyle and would enjoy a considerable energy savings with its use.
What is a Tankless Water Heater?
Tankless water heaters, also called “Instantaneous” or “On-Demand” water heaters, provide hot water only as it is needed. Traditional tank-type water heaters produce hot water all the time, whether it is needed or not. This causes standby energy losses that cost you money, all day, every day, all the time.
How do Tankless Water Heaters work?
Tankless water heaters heat water directly, without the use of a storage tank. Therefore, they avoid the standby heat losses associated with tank type water heaters. When a hot water valve is turned on, cold water travels through a pipe into the tankless unit. In an electric tankless water heater (like the one I installed in my home) an electric element heats the water. In a gas-fired tankless water heater a gas burner heats the water. As a result, tankless water heaters deliver a constant supply of hot water. How many times has someone in your home “used all the hot water”? That no longer happens with a tankless system. You don't need to wait for a large storage tank to fill up with enough hot water. Tankless systems make hot water for as long as there is a demand (a hot water valve is turned on). Typically, tankless water heaters provide hot water at a rate of between 2 to 5 gallons per minute. Typically, gas-fired (propane or natural gas) tankless water heaters will produce higher flow rates than the electric tankless water heaters will. Some of the smaller tankless systems cannot supply enough hot water for simultaneous, multiple uses in large households. For example: taking a shower and running the dishwasher at the same time can stretch a smaller tankless system to its limit. To overcome this problem, you can install a “whole house” type tankless water heater or install two or more tankless systems, connected in parallel for simultaneous demands of hot water. You can also install separate tankless water heaters for individual appliances, such as a clothes washer or dishwater, as these can consume a large volume of hot water in a short time.
Selecting a Tankless Water Heater
Before buying a tankless water heater, you must consider the following three things:
1. Fuel Type
2. Location, Size and Demand
1. Fuel Type The first thing that you'll need to decide when selecting a tankless water heater is the fuel type. You will need to select between an electric tankless water heater or a gas fired unit that operates on propane or natural gas. Lets discuss the electric operated models first. In my home, I have no natural gas or propane, and the utility company does not offer such in my area. My home is all electric, so my choice was pretty well made for me.
If you plan to purchase an Electric Tankless Water Heater, you must consider the electrical requirements of such a system. These are:
Voltage, Amperage, and Circuit Breaker
Voltage: Many of the tankless system retailers sell tankless units that will accommodate a variety of voltages, such as: 110V, 120V, 208V, 220V, 240V, and 277V.
Amperage: Different electric tankless water heaters will have various requirements in amperage draw. You will want to ensure that your electrical distribution panel (breaker box) can support the electrical demands of your electric tankless water heater.
Circuit Breaker: You must ensure that you have a circuit or circuits that will support your electric tankless water heater. It may be necessary to put your electric tankless system on its own circuit or circuits. This was necessary on my own home.
You should consult with a qualified, licensed electrician for more information.
If you plan to purchase a gas-fired tankless water heater, one must consider these two things: the Gas Type and the Venting Requirements. This is a bit more complicated than installing an electric system. If you are uncertain about any of these steps, it would be prudent to consult with a certified plumber or electrician:
Gas Type: You will first need to identify whether your type of gas is natural gas or propane. It is crucial that you examine your current gas line to ensure that it will meet the requirements of your new gas-fired tankless water heater. The requirements of the tankless water heater may exceed that of your existing conventional tank-style water heater.
Venting Requirements: Next, you will need to consider the venting requirements for your specific installation, since gas fired systems do require proper venting. There are a few important things to keep in mind when purchasing the gas venting accessories for your gas-fired tankless water heater.
First, be sure that you purchase only Category III stainless steel (UL1738 certified) venting for your gas-fired tankless water heater. "Type B" venting accessories are not acceptable. Also, be sure to check local building code to ensure that your specific needs will be completely met.
Additionally, many tankless water heater manufacturers offer complete venting "kits". Customers should evaluate the needs of their own specific installation to ensure that they will be getting all of the necessary gas venting accessories. Depending on where you will be installing the tankless water heater, a pre-made kit will probably not meet all of your needs. Ensure that you measure out the route your vent will take, and consider where the discharge will go through the wall or ceiling. Then consider the necessary clearances and also consider ample access to air for combustion, only then purchasing the appropriate gas venting pieces. *** NOTE: gas-fired tankless water heaters may still require a minimal electrical connection. Be sure to review your installation requirements for the unit you are considering for purchase. Now, the next item for consideration:
2. Location, Size, and Demand When deciding which system to purchase, you will need to consider just where you will need the hot water. Are you looking for a system that will just heat the water at one bathroom sink (called a single point application), an entire bathroom (called a multipoint application), or an entire house, apartment, or condo (called a whole house application)? It is very important to recognize the number of fixtures that require hot water. Each fixture has its own demands. The chart below illustrates the typical flow rates (demand) for some standard fixtures:
Bathtub: Flow rates average between 2 - 4 gallons per minute
Shower: Flow rates average between 1.5 - 3 gallons per minute
Kitchen Sink: Flow rates average between 1 - 1.5 gallons per minute
Laundry Sink: Flow rates average between 2.5 - 3 gallons per minute
Dishwasher: Flow rates average between 1 - 3 gallons per minute
The flow rate is especially important, since tankless water heaters generate a specific temperature rise based on the flow rate demanded. For example, a Stiebel Tempra 12 model, running on 240 Volt power, will raise the water temperature by 54°F above the ambient incoming water temperature at 1.5 gpm, or it will raise the water temperature by 36°F above the ambient incoming water temperature at 2.25 gpm, and by 27°F above the ambient incoming water temperature at 3.0 gpm, up to a high of about 125°F. A larger unit, like the Stiebel Tempra 36 model, running on 240 Volt power, will raise the water temperature by 92°F at 1.5 gpm, 92°F at 2.25 gpm, and 82°F at 3.0 gpm, above the ambient incoming water temperature, up to about 125°F. This means that if you are using a 1.5 gpm shower and a 1.5 gpm kitchen sink simultaneously, a total demand of 3.0 gpm, the Stiebel Tempra 12 model will raise the temperature 27°F, whereas the Stiebel Tempra 36 model will raise the temperature 82°F. Next, you should look at your incoming water temperature. If you live in a colder climate like Idaho or Michigan, your incoming water temperature will likely be much lower than if you live in a warmer climate like Arizona or Alabama. Your best bet is to find out how much temperature rise you will need in order for your hot water to reach the desired heat. For example: If the normal incoming water temperature for your shower is 65°F, and you are using a 2.0 gpm shower, and you want to raise that temperature to 115°F, you will want to look for a Tankless Water Heater that will provide at least a 50°F temperature rise at 2.0 gpm (115°F - 65°F = 50°F). However, if you anticipate additional simultaneous demand, such as the hot water from the dishwasher being used while someone is showering, you will need to add the dishwasher’s gpm to the shower's gpm in order to determine your overall gpm demand and then find the temperature rise necessary to meet your overall needs. All this may seem complicated… but it is not really hard if you take a notepad and tackle one paragraph at a time. Even easier: Most manufacturers have 1-800 help lines that can assist you in selecting the right model to suit your needs. And now, for the final consideration:
3. Application You may have a specific application or purpose in mind for your tankless water heater. Here are a few examples of the different models and their functionality for a specific application: Single Point Application A single point application is one where only one fixture, such as a dishwasher or a shower, will require a tankless water heater. These units can be quite small. Some of them are about the size of a shoe.Multi Point Application The "Flow Controlled" range of on-demand water heaters from Eemax are ideally suited to serve two points, like two sinks in close proximity. Eemax Series Two units are ideally suited for residential showers, entire bathrooms, smaller houses, condos, summer cabins and apartments. Whole House Indoor Use Larger ‘Whole House’ units are designed to serve an entire house, apartment, condo, or cabin, where multiple points of use will exist. This is what I purchased for my own home, and mine is about the size of a shoe box.Tankless Water Heater Installation and Maintenance
Proper installation and maintenance of your tankless water heater can optimize its energy efficiency. Proper installation depends on many factors. These factors include your climate as well as your local building code requirements. You should have a qualified, licensed plumbing contractor install your tankless water heater. Be sure your contractor first consults with the manufacturer’s installation instructions. Manufacturers usually provide the necessary installation and instruction manuals with the product. Your contractor should also contact your municipality for information about obtaining a permit, if necessary, and also about any state or local water heater installation codes. Many tankless water heaters have a life expectancy of more than 20 - 25 years. They also have easily replaceable parts that extend their life by many more years. In contrast, the traditional storage tank water heaters last only 10 to 15 years on average. Periodic water heater maintenance can significantly extend your tankless water heater's life and minimize any reduction of its incredible efficiency. Read your owner's manual for specific maintenance recommendations.
Tankless Water Heater Manufacturers
There are many manufacturers of tankless water heaters,,,,,,,,,,: Eemax, Noritz, Rinnai, Stiebel, Chronomite, Rheem, and Bosch to name just a few.