What are tankless water heaters?
Instant water heaters, also known as on-demand or tankless water heaters, heat the water as it passes through the heater, based upon the demand for hot water. No storage tank is needed.
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What are the advantages?
These units provide fast hot water, take up less space and eliminate the standby heat loss in a standard hot water tank.
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What are the disadvantages?
Tankless water heaters require more energy. You may need a licensed electrician to install an additional service panel to handle the load. Conventional water heaters typically require 4.5 kilowatts, while electrical tankless (gas is available) require 18-28 kilowatts.
What’s more, the additional power use may also require us to upgrade PGE equipment serving the home. Otherwise, lights may flicker and electrical devices could be damaged. Those costs would be billed to the customer.
Finally, electric tankless water heaters have important limits on water flow rate. Generally, the largest heaters can provide enough hot water to supply one shower or bath at a time and two sinks. Unless you use very low flow rates for showers, you may not be able to run dishwashers or clothes washers at the same time as a shower. If you need to use hot water for more than one purpose at a time, you may need two tankless heaters, which may require even more expensive upgrading of your electrical service capacity and of the distribution system.
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What are the energy savings?
There will probably be some energy savings if you use an electric tankless water heater, but the savings may be small in comparison with the added costs. Conventional water heaters are readily available with efficiency ratings of 93 percent. The efficiency of a tankless water heater may be slightly higher than 95 percent. We estimate that for the average user, savings would amount to about $15 per year.
The water heater’s location makes a difference. If you have a long distance between the water heater and where you use hot water, you’ll fill those pipes with hot water every time. Much of this water just ends up sitting in the pipe where the heat is wasted. Locating water heaters as close to the use as possible reduces this waste. This is often mentioned as an advantage of tankless heaters, however, you can also locate standard or undercounter water heaters close to the use.
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Are there alternatives to tankless water heaters?
If you are primarily interested in getting hot water faster, you can locate a standard tank close to where you need the water. The shorter the distance, the less time you'll have to wait (and the less hot water you’ll draw into pipes where it cools off).
If you are trying to save space, consider a small, undersink standard tank. They are available in sizes as small as five gallons, but you'll probably want to find a 20-gallon tank for most uses.
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When does tankless makes sense?
The best application for a tankless water heater is when there’s a long hot water pipe run from the existing water heater and there's not enough room for a small tank. If this is the case, find the smallest model that meets your needs. If your main need is to supply a shower, install a low-flow showerhead. If you just have a sink that needs hot water, you can use a small “point-of-use” tankless heater.
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