Green Building Elements: Tankless Water Heaters
Photo Credit: Univ of Alberta Creative ServicesNext to bulding heating and cooling, water heaters are the largest energy consumers in most homes. But, with a conventional water heater, much of the energy is spent on keeping the heated water from cooling off while it sits, waiting to be used. Tankless water heaters don't have these standby losses, and can be a much more efficient choice in some circumstances.
Tankless water heaters have no hot water storage (hence tankless), but can quickly raise water temperature by as much as 50 degrees F (~30 degrees C). They can do this with a flow rate ranging from 4 gallons per minute (GPM) to as much as 9 GPM. Tankless heaters are also much smaller than conventional water tank heaters, which can be a consideration for smaller homes where space is at a premium.
Depending on usage patterns, a tankless water heater can provide hot water much more efficiently than a regular tank heater. One manufacturer's information lists an annual operating cost (based on 2004 prices) of $166 for their tankless heater versus $210 for a conventional natural gas water heater, and propane and electric conventional heaters are even more expensive to operate.
Tankless water heaters can allow "endless showers." Since the water is being heated as it is needeed, there is no concern about running out of hot water, while a conventional tank heater has a capacity, after which the hot water runs out and water that has entered the heater tank needs to be heated
Tankless heaters may not be for everyone, however.
Supply water temperature can be a factor. Regions with cold winter ground temperatures may have incoming water that is 40-50 degrees F, which may not be able to be adequately heated for hot water needs. More temperate locations will likely be better for tankless water heater installations.
Tankless water heaters also have a much larger fuel supply requirement. In order to provide such a drastic temperature change, simple physics dictates that they need to use a lot of energy very quickly. Over the course of its life, the tankless heater doesn't use as much fuel as a conventional water heater, but when it uses fuel, it uses a lot of it very quickly. This can make retrofitting a tankless heater into an existing home difficult, because the gas line to the existing water heater may not be large enough to supply the needed gas for a tankless heater.
Are they right for you? As I'm increasingly fond of saying, it depends. A home for a larger family where multiple water uses (more than one shower at a time, washing clothes or dishes while showering, etc.) may put more demand on the system than it is able to supply hot water for. But a home for a single individual or a couple who are careful about not crossing their water use, they may be a way to have significant energy savings.
tankless water heaters can deliver really big savings if, like me, you have hot water radiators heating your house, or if you have radiant heating. I have a heat exchanger next to the unit heats the whole house as well as the domestic hot water. This cut my gas consumption by about 50% over the old water heater and inefficient furnace. However at a $9,000 cost it will take a few years to pay off.
More info here:
http://www.treehugger.com/files/2006/02/cut_your_gas_co_1.php
this is one of the reasons i wished I owned instead of rented.
If is abour time that we all started saving money and helping the enviroment. Go get more information on tankless water heaters go to
http://www.etankless.com
We are on our second tankless heater in 15 years. The first one was a Paloma, and it died when a little water remained in it after we had drained our pipes to go away and it froze. The second one is a Bosch/Aquastar. It puts out more hot water than the Paloma, but it doesn’t work as well in the winter. This problem could be solved if we ran the pipes through the woodstove first. Tankless sytems work best if you can use a solar water heater to preheat the water before it goes to the tankless. This is one thing missing from our system, that we hope to upgrade soon. My partner hates the tankless and wants to change, but I won’t let him. Also, they make more expensive models that can meet higher demands. We can’t shower and wash dishes at the same time. Our Aquastar is the biggest source of propane use we have in our home.
A friend suggested stacking two tankless heaters together to improve the winter issue. One tankless would serve to preheat the water, in order that the second one could further heat the water enough. This is an expensive option, and I am not sure what would be lost by the increased propane usage.